Modifiable musculoskeletal factors and their association with shoulder function in adults: A systematic review of risk and association

Modifiable musculoskeletal factors and their association with shoulder function in adults: A systematic review of risk and association | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Systematic Review Modifiable musculoskeletal factors and their association with shoulder function in adults: A systematic review of risk and association Sonia Briel, Corlia Brandt, Benita Oliver, Franso-Mari Olivier This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-4555953/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract Objective: The objective of this systematic review of etiology and risk was to determine the association between modifiable musculoskeletal factors and shoulder dysfunction in an adult population. Background: There is still a paucity of evidence in the literature on shoulder function and the influence of modifiable musculoskeletal factors on function. The present study aimed to explore current and past research on all reported modifiable musculoskeletal factors to clarify the multifactorial etiology of shoulder dysfunction in an adult population. Methods: The methodology and meta-analysis process were performed as detailed in the JBI Reviewer’s Manual for Etiology and Risk, and the following guidelines were used according to the PRISMA (Preferred Items for Systematic Reviews and Meta-Analysis) statement. When a meta-analysis of the data was not possible, the SWiM (synthesis without meta-analysis) approach was used for the synthesis of pooled modifiable musculoskeletal factors. The outcome measure considered was shoulder dysfunction. The exposure parameters measured were modifiable musculoskeletal factors leading to the development of shoulder dysfunction. Patients aged between 18 and 75 years were included. A total of 7628 studies were identified worldwide through searching 12 databases. The results yielded by 91 studies were included in the systematic review. The risk of bias was low for 88 studies. Both females (2441) and males (3117) were included. The systematic review included cross-sectional and longitudinal studies investigating most sporting subpopulations (swimming, rugby, weightlifting, wheelchair, volleyball and baseball; 1003 participants) and members of the general population (4651). Pooling of the results into five meta-analyses was possible. Results: The results revealed that affected musculoskeletal factors led to a decrease in the strength of shoulder dysfunction during external rotation, with I 2 = 0 indicating a large positive effect size of 0.59 (p = 0.00), a decreased external versus internal muscle strength ratio, with I 2 = 46 indicating a large negative effect size of -0.69 (p = 0.002); decreased flexibility of the posterior capsule, with I 2 =0 indicating a small negative effect size of -0.0 (p = 0.45); decreased internal rotation, with a large negative effect size of -1.00 (p = 0); and a glenohumeral internal rotation deficit. Participants were 1.29 times more likely to develop shoulder dysfunction in the presence of decreased external rotation strength. Discussion: A comprehensive evaluation of the shoulder joint should include all identified musculoskeletal factors of the present systematic review at one point in time. Modifiable musculoskeletal factors include the strength of the external and internal rotators; the strength ratio of the external rotators: internal rotators; the internal rotation range of motion movement; the total range of motion; glenohumeral internal rotation deficit; pectoralis minor muscle length; posterior capsule and the glenohumeral posterior musculature flexibility; and scapular stabilizer strength and strength ratios. This protocol has been registered in PROSPERO (CRD 42021261719). Physical Medicine & Rehab External internal strength GIRD Shouder dysfunction strength ratios. Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Figure 10 Figure 11 Key Points Decreased external rotation strength, decreased external versus internal rotation strength ratios, decreased internal rotation and GIRD predispose a shoulder to dysfunction. All musculoskeletal factors identified with this systematic review should be addressed at one point in time during both the evaluation and rehabilitation process. 1. Introduction Shoulder pain affects 16–21% of the general population [ 1 , 2 ]. In addition to being highly prevalent, shoulder pathology is potentially a debilitating and challenging diagnosis [ 3 ]. Various researchers have concluded that the rotator cuff is responsible for shoulder pain among patients [ 4 – 6 ]. In their study of imaging pathology, the rotator cuff was concluded to be the main pain driver in shoulder pain, determined to be as high as 50% on ultrasound imagery and 65% on magnetic resonance arthrogram [ 6 ]. The pathogenesis of rotator cuff injuries (RCIs) is multifactorial and controversial, but the shape of the acromion is still thought to be a contributing factor to the development of shoulder pain [ 7 ]. The confirmed findings that tears of the supraspinatus muscle are located mainly within the tendon or on the articular side of the joint contradict the acromial impingement syndrome model [ 8 – 10 ]. The force coupling mechanism of rotator cuffs can be disrupted by weakening or injury to the rotator cuff muscles [ 11 , 12 ]. This destabilization of the humeral head on the glenoid cavity occurs when the muscle length and force are abnormal therefore, arthrokinematics are disrupted [ 11 , 12 ]. Abboud and Soslowsky [ 13 ] concluded that altered force couple vectors of the rotator cuff can lead to instability and thus destabilization of the humeral head on the glenoid cavity. An imbalance in this muscular system might be conducive to the development of structural damage in the glenohumeral joint [ 14 ]. The supraspinatus is the first muscle to activate during elevation [ 15 ]. The compressive force provided by the supraspinatus contributes to the stability of the humeral head in the glenoid cavity [ 16 ]. In their electromyography (EMG) study, Abboud and Soslowsky [ 13 ] reported that from 60° to 150° in the abduction plane of movement, contractions of both the subscapularis and the infraspinatus occurred. The subscapularis muscle not only functions as a humeral head depressor but also stabilizes the humeral head and functions as an internal rotator of the humeral head [ 17 , 18 ]. Additionally, other specific musculoskeletal factors (shortening and tightness of the posterior capsule, pectoralis minor, latissimus dorsi, short head of the biceps and subscapularis) have been independently identified by various researchers as contributing factors to the development of shoulder pain [ 19 – 21 ]. The anatomical attachment of the short head of the biceps brachii to the anterior tip of the coracoid process can contribute to scapular dyskinesis [ 22 ]. Posterior capsule tightness and a decreased range of motion (ROM), specifically the internal range (IR) of motion, have been associated with an increased incidence of shoulder pain [ 23 ]. Shortening and hypertrophy of the posterior capsule have been associated with decreased internal rotation and resultant anterior migration of the humeral head [ 24 – 26 ]. Factors contributing to the development of glenohumeral joint internal rotation deficit (GIRD) include posterior capsule tightness and stiffness of the posterior muscle tendon unit [ 27 ]. A preliminary search of the JBI Evidence Synthesis, Cochrane Database of Systematic Reviews, MEDLINE (PubMed), and PROSPERO databases was conducted using the following search terms: rotator cuff, shoulder, scapulothoracic joint, musculoskeletal, GIRD, and subacromial impingement syndrome (SIS). To the best of our knowledge, only two systematic reviews were conducted that identified potential risk factors predictive of shoulder pain Hill [ 28 ] conducted one and the other was by Keller [ 29 ]. In their systematic review, Hill [ 28 ] explored risk factors such as GIRD, internal and external rotation strength of the rotator cuff and clinical instability leading to shoulder pain in a subpopulation of swimmers. In their systematic review with meta-analysis, the authors investigated only GIRD and increased external rotational gain as risk factors favoring injuries in a subpopulation of overhead athletes [ 29 ]. In their study on volleyball players, Reeser [ 30 ] stated that an understanding of modifiable risk factors is essential for preventing shoulder pain and providing optimal care for players presenting with shoulder pain. Lewis [ 31 ] concluded that considerable deficits still exist in our current understanding of rotator cuff-related shoulder pain (RCRSP). These include (1) the exact origin of symptoms, (2) the determination of more accurate diagnostic labels, (3) better epidemiological studies of symptomatic shoulder pain patients, (4) more accurate establishment of symptomatic tissues to target treatment, and (5) determination of the best treatment modalities for symptomatic shoulder pain patients [ 31 ]. His main conclusion was that there is a need for ongoing research to seek a better understanding of the underlying etiology, better assessment models and the development of better management protocols [ 31 ]. There is a need for clarification and a better understanding of the influence of musculoskeletal factors and their association with shoulder function. The current models used in the diagnosis of shoulder dysfunction might thus be outdated and not appropriate or applicable in clinical practice. The overall aim of this systematic review was to determine modifiable musculoskeletal factors and their associations with shoulder function in adults aged between 18 and 75 years. The purpose of this review was ultimately to identify a cluster of musculoskeletal tests to determine the risk factors associated with shoulder dysfunction. 2. Methodology This systematic review was conducted in accordance with the JBI methodology for Systematic Reviews of Etiology and Risk [ 32 ]. 2.1 Inclusion criteria 2.1.1 Participants Studies including females and males globally with and without shoulder dysfunction aged between 18 and 75 years were included in this review. Studies on participants from both the general population and the athletic population were included (athletic subgroups could be classified as any sporting fraternity, e.g., overhead sport, tennis, cricket or underhand such as rugby). Studies involving participants with postoperative shoulder dysfunction were not included. 2.1.2 Exposure of interest Studies that investigated modifiable musculoskeletal factors impacting the biomechanical and arthrokinematical functioning of the shoulder joint, as independent variables, were explored and included in the study. Only modifiable musculoskeletal factors were included, which were defined as the musculoskeletal and capsular factors listed below; therefore, factors such as bony factors were excluded. The following modifiable musculoskeletal factors were included: Pectoralis minor, latissimus dorsi and rotator cuff (supraspinatus, infraspinatus, teres minor, and subscapularis) muscle lengths were measured with a caliper, goniometer or tape measure. The strength of the pectoralis minor, latissimus dorsi, and rotator cuff (supraspinatus, infraspinatus, teres minor, and subscapularis) muscles was measured with a dynamometer, and the results included derived measurements such as balance/imbalance of strength ratios of the rotator cuff, e.g., expressed as ratios of internal/external versus external/internal rotators; Capsular flexibility, such as anterior and posterior capsule length measured using a goniometer or inclinometer; The shoulder range of movement was measured using a goniometer or inclinometer. 2.1.3 Outcome The outcome of interest was shoulder dysfunction. Shoulder dysfunction, the dependent variable, included any one or a combination of the following: the presence of discomfort, measured with subjective patient self-reports; pain, measured and reported on the visual analog scale (VAS) or on the numeric pain rating scale (NPRS); or dyskinesis, measured though kinematic analysis. Shoulder dysfunction was also reported with outcome measurement questionnaires such as but not limited to the Shoulder Pain and Disability Index (SPADI). 2.1.4 Type of study Both observational (cross-sectional, case‒control, prospective and retrospective and longitudinal cohort studies; case series and case reports), analytical and descriptive studies were included in this review. Experimental and randomized control trials were excluded from the study because only the association of dysfunction of the shoulder joint with modifiable musculoskeletal factors was established. 2.1.5 Search strategy The methodology and meta-analysis process, as detailed in the JBI Reviewer’s Manual for Etiology and Risk [ 33 ], were followed, and the guidelines proposed by the PRISMA (Preferred Items for Systematic Reviews and Meta-Analysis) statement [ 34 ] were followed. The Population, Problem, Intervention, Comparison or Control, and Outcome (PICO) methodology [ 35 ] was adapted to fit the study design of our systematic review to Population, Etiology, and Outcome (PEO). The research question and, subsequently, search terms were developed around the PEO concept. The search strategy included both published and unpublished studies. A three-step approach was followed. First, an initial limited search of PubMed Central and CINAHL (EBSCOhost) was undertaken to identify articles on the topic. The text words used were from the titles and abstracts of relevant articles, and the index terms used to describe the articles were used to develop a full search strategy for PubMed Central (Appendix I). Second, for the main review, all identified keywords were explored using both MeSH and text words and were appropriately adapted for each database. Third, all the reference lists of all the studies selected for critical appraisal (backward citation tracking) were screened for additional studies. Forward citation tracking using Google Scholar and Academia.edu was then performed for the identified studies. No restriction was placed on language, but the age was limited to adults aged eighteen years and older. Studies published in all languages were included. An in-depth search across twelve databases was conducted from inception to the end of March 2023, and the relevant articles were included. An updated search was conducted from the beginning of April 2023 to the 6th of March 2024, and the applicable articles were imported. The databases searched included PubMed (Advanced), MEDLINE, MEDLINE COMPLETE, Masterfile, and SPORTDiscus via EBSCOhost; the Cumulative Index to Nursing and Allied Health Literature (CINAHL); the Physiotherapy Evidence Database (PEDro); and the Web of Science and Scopus (Elsevier). The information sources of unpublished and gray literature included Open Gray, Gray Matter, and MasterFile Premier (EBSCO) (Appendix I). All the included and excluded studies are depicted by means of the PRISMA flowchart (Figure I) [ 34 ]. 2.1.6 Study selection Following the search, all identified citations were collated and uploaded into EndNote X9.3.3 (Clarivate Analytics, PA, USA) (2021), after which duplicates were removed. Potentially relevant studies were retrieved in full, and their citation details were imported into the JBI System for the Unified Management, Assessment, and Review of Information (JBI SUMARI) [ 33 ]. Titles and abstracts of the uploaded articles were subsequently reviewed by two independent reviewers for assessment against the inclusion criteria of the review. 2.1.7 Data extraction All studies, regardless of the results of their methodological quality, underwent data extraction, and some were synthesized into meta-analyses. Data were extracted from the studies included in the review by two independent reviewers using standardized JBI SUMARI data extraction tools [ 33 ]. The extracted data included specific details about the population (participant characteristics, age, sport discipline or sedentary), study methods, aim, context, exposure of interest, study setting and location (country), and outcomes of significance to the review question (Table of Characteristics-Online Resource 2 and Figs. 2 , 3 ). No disagreements arose that required the intervention of the third reviewer. 3. Assessment of Methodological Quality Eligible studies were critically appraised by two independent reviewers (SB and FM-O) at the study level for methodological quality in the review using standardized critical appraisal instruments from the JBI [ 33 ]. The numerical scores for the analytical cross-sectional studies were scores out of eight and those for the eligible cohort studies out of eleven ( Appendix 3 ). Methodological quality was deemed high overall for the included studies included in the meta-analyses and for both the eligible analytical cross-sectional and the eligible cohort studies. Two studies, Skazalski [ 36 ] and Peckitt [ 37 ], were of lower methodological quality because they did not state how confounding factors were dealt with ( Appendix 3 ). Methodological quality was documented throughout the appraisal process. All studies, regardless of their methodological quality, underwent data extraction, and some studies were synthesized and combined into meta-analyses (Figs. 4 , 5 , 8 , 9 , 11 ). All the data used for generating the meta-analyses were taken from both the eligible analytical cross-sectional and eligible cohort studies. The data were subjected to double entry by two reviewers (SB and FM-O). The results of the critical appraisal were reported in tabular format with accompanying narratives highlighting the main findings of individual studies (Online Resource 1) and in the Table of Characteristics (Online Resource 2). 4 Data synthesis Clinical, methodological, and statistical heterogeneity was determined [ 38 ]. Risk ratio (RR) and odds ratio (OR) data were extracted from the primary longitudinal studies included (Table I), answering the proposed study questions concerning the risk of shoulder dysfunction in the present systematic review. When the RR was unavailable, it was calculated using the SPSS Statistics 28.01.1.1 (15) IBM Corp., Armonk, NY, USA) package, and the results obtained were imported into JBI SUMARI for the generation of a meta-analysis (Fig. 2 ). Studies that reported the mean and standard deviation of the identified primary studies reporting on the cases and on the controls were included in the proposed meta-analysis (Figs. 4 , 5 , 8 , 9 , 11 ). The effect size was calculated to measure the strength of association between the groups of the identified studies and was expressed as the standardized mean difference (SMD) for continuous data for all groups. The 95% confidence intervals were calculated for the analysis. Study data were pooled in statistical meta-analyses using the JBI SUMARI to increase the accuracy of the derived overall effect size [ 33 ]. Cohen’s d method was employed to estimate the pooled SMD and weight using an inverse variance method [ 39 ]. Due to the inherent suspected heterogeneity across studies, a random effects model (using the DerSimonian and Laird method) was used to estimate the RR and the SMD. Five comparative meta-analyses were composed using the JBI SUMARI [ 33 ]. The effect sizes (RR) and (OR) were extracted to determine the association between shoulder dysfunction and modifiable musculoskeletal factors (Fig. 4 ). Meta-analysis (1): The risk ratio between musculoskeletal modifiable risk factors and internal rotation (IR) and the development of shoulder dysfunction. The effect size expressed as the standardized mean difference (SMD) was used in the etiology meta-analyses (Meta-analysis 2–5). Meta-analysis (2): Studies that reported on the external rotation strength of the cases and the controls measured using either a handheld dynamometer with isometric testing or isokinetic dynamometry with isokinetic testing were selected. Meta-analysis (3): Studies reporting on the strength ratio of the external rotators (ERs): internal rotators (IRs) of the cases and the controls were included. Meta-analysis (4): Studies reporting on the internal range of movement) measured using an inclinometer in degrees of the cases and the controls were included in the analysis. Meta-analysis (5): Studies reporting on the GIRD of the cases and the controls were included in the analysis. Heterogeneity within the meta-analysis of the results was statistically tested using the I 2 test. Sensitivity analysis was also conducted to explore the impact of the included and excluded studies on the heterogeneity of the meta-analyses. The pooled results of the meta-analyses are graphically presented with forest plots (Figs. 4 , 5 , 8 , 9 , 11 ). For funnel plot generation, two variables are needed: the standard error and the effect size. The standard error was calculated in SPSS using the available sample sizes of the different studies and the effect sizes derived from the forest plot data constructed in JBI SUMARI [ 33 ]. A funnel plot assessing publication bias was generated in SPSS. Statistical analysis using Egger’s test was also performed [ 40 ]. When a meta-analysis of the data was not possible, the SWiM (synthesis without meta-analysis) approach was used for the synthesis of pooled modifiable musculoskeletal factors [ 41 ]. 5 Study characteristics A total of 7628 studies were identified through searching 12 databases (Fig. 1 ). An additional eight records were identified through alternative sources (gray literature, thesis and reference lists of articles sourced) and added to the potentially applicable studies. Of these, 3524 duplicates were removed, while another 1253 records were removed for not fulfilling the inclusion criteria. The remainder of the 2870 records were screened by the primary reviewer. A total of 2070 records were excluded because they were not deemed applicable to the review question. Two hundred and fifty-one studies were identified and found to be suitable for meeting the inclusion criteria, and the detailed results were imported into the JBI SUMARI [ 33 ]. The updated search, conducted from the 1st of September 2022 through the 6th of March 2024, yielded one suitable article that met the inclusion criteria of the present systematic review and was incorporated into the present study. The studies were critically screened in a two-step process within the JBI SUMARI [ 33 ]. First, two independent reviewers (SB and FM-O) screened all the studies at the abstract and title levels, and if deemed appropriate for the review question, the full texts were critically screened. Sixty studies were excluded when scrutinized during the abstract and title screening because they were deemed not applicable to the inclusion criteria for the current systematic review (Figure I). The reasons for the exclusion of both title and abstract and for full-text studies that did not meet the inclusion criteria were recorded and are reported in a table of excluded studies ( Appendix 2 ). No disagreements arose between the reviewers at any stage of the study selection process, and there was no need for intervention by the third reviewer. The results yielded 91 studies that were included in the systematic review. The characteristics of the included studies are described in the Table of Characteristics (Online Resource 2). The study designs included were as follows: quasi-experimental = 2; case control = 2; diagnostic test accuracy = 3; cohort = 14; case series = 2; case report = 1; prevalence = 1; text and opinion = 5; and analytical cross-sectional = 46. Sixteen studies provided sufficient data to be pooled into meta-analyses. Age ranged from eighteen years to seventy-five years. A visual depiction of the countries where the studies were conducted can be found in Fig. 2 . 6 Assessing confidence in the findings: To assess the association between shoulder dysfunction and the presence of modifiable musculoskeletal factors, the following studies were included in the current systematic review [ 42 – 61 , 36 – 37 ]. Several screening instruments, such as the visual analog scale (VAS) [ 58 , 62 ], overuse injury questionnaire [ 36 ], Nordic [ 63 ] and Penn Shoulder score [ 64 ], were used for reporting the incidence of shoulder pain in the identified primary studies. Due to the heterogeneity of the different pain and dysfunction scales used for reporting pain, the data could not be pooled into a meta-analysis. The incidence of shoulder pain ranged from 27.2% [ 36 ] to 55% [ 63 ] in the presence of identified modifiable musculoskeletal factors. The clinical symptoms and discipline (sport, e.g., tennis; sedentary, e.g., no sport) studied and identified are summarized in the Table of Characteristics (Online Resources 2) and in Fig. 3 . The etiology of the modifiable musculoskeletal factors causative of shoulder dysfunction was explored with SMD. The Grading of Recommendations, Assessment, Development, and Evaluation (GRADE) [ 65 ] approach for assessing confidence in the quality of evidence was used, and a summary of findings (SoF) (Online Resource I) was created. The outcomes reported were SMD (95% CI) and the level of evidence (LOE) determined by the Oxford grading system. Studies were identified across different subpopulations, ranging from overhead sporting activities to activities of daily living (Fig. 3 ). Data from the primary studies were collected across various sporting fraternities, such as tennis [ 53 ], baseball [ 66 ], volleyball [ 36 ], handball [ 60 ], gymnastics (54], weight training [ 55 ], rugby [ 58 ], wheelchair users [ 67 – 68 ] and a sample of members of the public [ 48 ] (Fig. 3 ). Participants who were tested via physical testing (n = 5558), both female and male participants (F = 2441) and (M = 3117) were included [ 42 – 61 , 36 – 37 ]. One study consisted of only a questionnaire (n = 5250) completed by both female and male participants [ 63 ]. 7 Results The Summary of Findings (SoF) Table I and (SoF) (Online Resource I) reflect the results of the included primary studies for the meta-analyses performed. The outcome variables, namely, shoulder dysfunction, where causation was determined, were labeled case (dysfunctional shoulders) and control (non-dysfunctional shoulders). To determine the associations between the exposure variables, namely, the modifiable musculoskeletal risk factors ROM, ER and IR and muscle strength (ER and IR), and the outcome variable (shoulder dysfunction), the risk ratio (RR) and odds ratio (OR) were used. 7.1 Shoulder dysfunction 7.2 Risk analysis The strength of the association between the development of shoulder dysfunction and the presence of modifiable musculoskeletal factors was explored using the RR and OR (Table I and Fig. 4 ). The extracted results provided by four studies [ 70 , 58 , 36 , 56 ] revealed an association between the development of shoulder dysfunction and the incidence of modifiable musculoskeletal factors (Table I). The results are expressed from the primary studies pooled into the RR meta-analysis (Fig. 4 ). concluded that participants were at a 1.21-fold increased risk of developing shoulder pain in the presence of decreased IR [ 70 , 58 , 36 ] and that participants were at a 1.08-fold increased risk of developing shoulder pain in the presence of increased ER (Table I). Determining the association between strength and shoulder dysfunction, the OR calculation revealed an increased incidence of 1.29-fold increased risk for patients to present with a supraspinatus tear in the presence of decreased ER strength (Table I) and a 1.18-fold increased risk for presenting with a supraspinatus tear in the presence of decreased abduction strength (Table I). The risk of developing shoulder dysfunction was 1.026 times greater in participants presenting with GIRD [ 71 ] (Table I). A positive association was detected between IR ROM differences [ 70 , 58 ] and an increased incidence of pain in the shoulders of participants, according to the risk ratio calculated in meta-analysis (1) (Table I). A positive association was determined between decreased ER and abduction strength and a supraspinatus tear [ 56 ] (Table I). A positive correlation was determined between the development of shoulder dysfunction and GIRD [ 71 ] (Table I). Only the ROM primary risk association studies could be pooled into a meta-analysis. Table 1 (SoF) Risk analysis (RR) and (OR) reported for risk variables of the included primary longitudinal studies. Author Association measurements (RR/OR) 95% CI Risk factors and incidence of shoulder dysfunction Olivier et al., 2020 Longitudinal cohort RR 1.99 (1.40. 2.59) Decreased ROM (IR). Shoulder dysfunction = 28% McDonough et al., 2014 Longitudinal cohort RR 0.42 (-0.21. 1.04) Decreased ROM (IR). Shoulder dysfunction = 36% Skazalski et al., 2020 Longitudinal cohort OR 1.08 (0.99. 1.17) Increased ROM (ER). Shoulder dysfunction = 27.1% Miller et al., 2016 Longitudinal cohort OR 1.18 (1.06. 1.32) Decreased ABD strength and supraspinatus tear. Shoulder dysfunction = 39% Miller et al., 2016 Longitudinal cohort OR 1.29 (1.14. 1.48) Decreased ER strength and supraspinatus tear. Shoulder dysfunction = 39% Olivier et al., 2018 Longitudinal cohort OR 1.001 (1.026. 1.052) GIRD and shoulder pain. Shoulder dysfunction = 39.2% RR= risk ratio; OR= odds ratio; ROM=range of motion; IR= internal rotation; ER= external rotation; ABD= abduction; GIRD= glenohumeral internal rotation deficit . An increase in the risk of developing shoulder dysfunction of 1.26 times was observed in the presence of decreased IR, as shown in Fig. 4 . 7.3 Etiological analysis The SMD was used for the reported effect size of the identified modifiable musculoskeletal factors between the cases and the controls (SoF) (Online Resource I). For data collection from the primary studies used for the SMD calculations, measurements were extracted and documented in the following way: strength testing was conducted with either isometric dynamometry or using handheld dynamometers and reported in kilograms (kg) or Newtons (N) (SoF) (Online Resource 1). The results of the tests conducted with an isokinetic dynamometer (Cybex) were reported in Newtons/Kilograms (Nm/kg), and with manual muscle testing techniques, the Oxford grading scale was used. The ROM was measured using either a digital or plastic handheld or bubble inclinometer and was documented in degrees. In one study, digital photography was used for measurements of degrees. Kinematic analysis was performed, and the results were documented using inertia motion sensors. For muscle length measurements, calipers, a rigid plastic square, a carpenter square, or a flexible tape measure were used, and the results are reported in centimeters (cm). The etiology of the development of shoulder dysfunction was based on the following modifiable musculoskeletal factors: the rotator cuff musculature, the strength ratio of the inferior cuff (external versus internal strength), the supraspinatus muscle, differences in the length of the pectoralis minor muscle, the latissimus dorsi muscle length and posterior capsule flexibility. Specifically, the ROM, IR, GIRD, posterior capsule tightness (PCT), horizontal adduction (Hadd), total range of motion (TROM), external rotation gain (ERG), external rotation deficit (ERD) of the glenohumeral joint, pectoralis minor muscle changes and scapular dyskinesis were reported. The previously mentioned exposure variables have been highlighted in this review in the findings and discussion sections (Online Resource I) [ 30 , 36 , 37 , 42 , 44 – 54 , 56 – 62 , 64 , 66 , 68 – 69 , 70 – 82 ]. The modifiable musculoskeletal factor variables were compared between the cases and controls among both females and males in the included primary studies. 7.4 Muscle Strength 7.5 External rotation strength The second meta-analysis (Fig. 5 ) reported the ER strength of the cases and the controls, and enough homogeneity was present between the studies, using the means and standard deviation (SD) to be pooled into meta-analyses. The participants were measured with isokinetic and isometric dynamometers. The SMD was calculated using the random-effects model for ER strength. In meta-analysis (2), a high heterogeneity of I 2 = 74 and a moderate effect size of 0.54 (95% CI, 0.22–0.85) with a significance of P = 0.001 were present, with the results favoring increased ER strength in the controls (Fig. 5 ). Potential sources of heterogeneity could be attributed to age differences between the participants, sex differences and the different testing methods employed. After sensitivity analysis was conducted, the heterogeneity decreased (I 2 = 0), and a small negative effect size of -0.29 (95% CI, -0.80-0.40) and a nonsignificant difference (p = 0.85) were detected (Fig. 6 ). The results still favored stronger ER strength values in favor of the controls. Publication bias was assessed using a funnel plot (Fig. 7 ), and no publication bias was detected. In an effort to reduce heterogeneity, a study testing isokinetic external rotator cuff strength [ 60 ] (SoF) (Online Resource I) was removed from the meta-analysis. To further reduce heterogeneity, a sub analysis of studies with similar sample sizes was performed [ 53 , 78 , 48 ]. (SoF) (Online Resource I) were constructed. The heterogeneity decreased to I 2 = 0%. The overall results still supported the use of stronger external rotators for the controls, with a large positive effect size of 0.59. 7.6 External (ER): Internal (IR) strength ratio The following meta-analysis (3) in Fig. 8 presents the ER:IR strength ratio between the cases and the controls of the included pooled studies. Pooling of studies investigating ER:IR strength ratios between the cases and the controls made it possible to employ the means and SDs to estimate the SMD with a random-effects model in a meta-analysis. With a statistically significant presence (p = 0.002), medium heterogeneity (I 2 = 46) and a large negative effect size of -0.69, as depicted in Fig. 8 , overall lower ER:IR strength ratios are shown to favor these patients. 7.7 Internal Rotation ROM Meta-analysis (4) revealed the difference in the IR ROM between the cases and the controls (Fig. 9 ). Pooling of studies investigating internal rotation between the cases and the controls was possible by employing the means and SDs to estimate the SMD with a random-effects model in a meta-analysis (Fig. 9 ). Even though a high level of heterogeneity was present (I 2 = 77), a large negative effect size of -0.62 (95% CI, -0.95:0.28) was determined, favoring the cases. According to the sensitivity analysis (Fig. 10 ), after removing participants from larger sample sizes and grouping similar subgroups, such as tennis players together, less heterogeneity was demonstrated (I 2 = 0), with a large negative effect size of -1.00 (95% CI, -1.30: -0.70). The results still favored the cases [ 53 , 72 , 78 ]. 7.8 GIRD Meta-analysis (5) explored the GIRD of the cases (Fig. 11 ). When the means and SDs were pooled with the random effects model to determine the SMD, heterogeneity was not detected (I 2 = 0), with a small negative effect size of -0.10 (95% CI, -0.36:0.16) favoring the cases. 7.9 Muscle flexibility of the cases and the controls 7.10 Pectoralis minor The muscle length of the pectoralis minor muscle (PMm) was investigated in terms of the muscle indices; muscle shortening; muscle lengthening; muscle activity; muscle rest; and muscle length in different testing positions [ 30 – 31 , 57 , 64 , 67 , 70 , 72 , 75 , 82 – 92 ]. Two main physical examination-based measurements for the pectoralis minor muscle were identified and used by various authors in the study of both cases and controls: the pectoralis minor index (PMI) test described by Borstad [ 93 ] and the pectoralis minor length test (PMLT) described by Kendall [ 94 ]. Full details are available in (SoF) (Online Resource I) and (Table of Characteristics) (Online Resource 2). The results of the studies that investigated PMm flexibility could not be pooled into a meta-analysis due to heterogeneity in the measurement methods used. The characteristics of pectoralis minor were pooled together, and the results are summarized in tabular formats (Table of Characteristics) (Online Resource 2) and in (SoF) (Online Resource I.). A positive trend between changes in PMm flexibility and the cases has been established with the current systematic review. The derivation results are fully discussed in the discussion section. 7.11 Scapular kinematics Scapular kinematics, dyskinesis and EMG studies of the scapular stabilizers were performed by the following authors: [ 30 , 48 , 61 , 76 , 84 , 86 , 88 – 89 , 95 – 97 ]. The results are highlighted, discussed and tabularized in the “SoF” section (Online Resource I) and in the “Table of Characteristics” section (Online Resource 2). 8 Discussion 8.1 Association between modifiable musculoskeletal risk factors and the development of shoulder dysfunction This was the first systematic review, to the authors’ knowledge, to investigate multiple known modifiable musculoskeletal factors and their association with the development of shoulder dysfunction at one point in time. All currently available evidence was summarized, analyzed and methodologically appraised (Online Resources I, 2). The current systematic review included cross-sectional and longitudinal studies investigating numerous sporting populations (swimming, rugby, weightlifting, wheelchair sports, volleyball and baseball (1003 participants)) and members of the general population (4651). The studies included both females (2441) and males (3117). An increased risk of developing shoulder dysfunction in the presence of modifiable musculoskeletal factors was determined with the RR and OR analysis of the present systematic review (Table I). Risk analysis revealed that the incidence of both ROM and strength changes in the presence of modifiable musculoskeletal factors in dysfunctional shoulders [ 70 , 58 ]. The strength of the association between exposure and outcome was tested by pooling studies into several meta-analyses (Figs. 4 , 5 , 8 , 9 , 11 ). Very little bony support is provided to the glenohumeral and scapulothoracic joints, which are mainly controlled by contractile and noncontractile muscular forces [ 98 – 99 ]. Participants studied with EMG analysis and presented with subacromial impingement demonstrated decreased activation of the subscapularis-infraspinatus and supraspinatus-infraspinatus force couples and increased middle deltoid activation at the start of elevation (0°–30°) [ 100 ]. Recent research by Millet [ 101 ] proposed that in subacromial impingement syndrome, the force vector of the supraspinatus that counterbalances the upward directed force of the deltoid might be disrupted. Weakness and thus decreased proprioception of the infraspinatus disrupt the force couple of the rotator cuff and destabilize the glenohumeral joint on the glenoid [ 102 ]. These historical results will be discussed next considering the conclusions drawn from the current systematic review. 8.2 Strength Numerous authors [ 54 , 58 , 60 , 66 ] of the included primary studies used for the generation of strength meta-analyses agree that stronger external rotators contribute to shoulder stability and, in their opinion, lessen the chances of developing shoulder dysfunction. In primary studies conducted on the strength differences of nondysfunctional shoulders of overhead athletes and in a convenience sample of members of the general population, no difference in side-to-side strength was found [ 37 , 49 – 51 , 60 , 103 ]. Not all published data from identified studies reporting strength measurements could be used for pooling results due to methodological differences. A study by Wong [ 47 ] reported the normalized fatigue ratios and the peak ratios of cases and control participants, but due to the difference in measurement properties, the data could not be incorporated into strength meta-analyses. Their main conclusions reflected an expressed lower peak torque reached in concentric ER in the cases in comparison to the controls. The decreased strength of the external rotator as well as of the supraspinatus may be linked to pain inhibition as the causative factor. However, Lajtai [ 104 ] determined that atrophy of the infraspinatus was present in the painful shoulders of beachball volleyball payers. The difference in strength was a mean of 2.3 kg between the painful and nonpainful sides. A decrease in the cross-sectional area of the supraspinatus in the presence of painful shoulders was observed by Benitez-Martinez [ 105 ]. Therefore, the authors believe that the decreased muscle strength observed in the affected tissues (infraspinatus and supraspinatus) may be responsible for the decrease in strength observed in the ER, and the observed differences in strength may not be solely due to pain inhibition. Considering the overall conclusions reached from the strength meta-analyses (Fig. 5 , 8 ), strengthening the ER, especially through eccentric control of the ER in overhead athletes, might be advisable to offset strong IR. This prevents the development of ER fatigue with repetitive overhead throwing motions, predisposing an athlete to injury. Hence, it could be hypothesized that a stronger ER may be beneficial for shoulder stability in all healthy shoulders regardless of the activity performed. 8.3 Ratio of the ER:IR strength In the present systematic review, strength ratios were explored in most populations, including members of the general population. The results of the primary studies [ 53 , 58 , 106 ] reflected higher strength ratios to favor the controls in both overhead, underhand and members of the general population (Fig. 8 ). Even though some caution should be given to the conclusions, given the presence of a statistically significant (p = 0.002) medium effect size, a higher ER:IR ratio was found in favor of the controls. Although not pooled into a meta-analysis, the results obtained in another systematic review [ 108 ], which was not pooled into a meta-analysis and was conducted on an overhead athletic population, concurred with the results of the current SR, which showed that a low strength ratio (ER:IR) is predictive of the development of shoulder dysfunction. These findings were reiterated in previous studies of overhead athletes by Saccol [ 108 ], who concluded that no significant difference in strength was present in the isometric ER:IR strength ratios in asymptomatic athletes. A different testing procedure was employed by Peckitt [ 37 ] in that they tested cricket players preseason and in-season to monitor strength changes present at baseline and those developed during season on both the dominant and nondominant sides. Therefore, the data could not be incorporated into any of the strength meta-analyses because they did not fit any of the case or control categories of the present systematic review. Their main conclusion was that the dominant ER:IR strength ratio was lower, with a mean ER of 0.71 (0.13) versus an IR of 0.93 (0.21) at baseline testing of players predisposed to developing arm trouble in-season. The results can be found in the Table of Characteristics (Online Resource 2) and (Online Resource I). In contrast to previous reports, McDonough [ 58 ] investigated the dynamic control ratio (DCR) of the IR:ER in rugby league players. The authors tested the eccentric internal (Ecc/IR) and concentric external (Conn/ER) rotator cuff strengths in the 90-degree abducted position via isotonic testing of the inferior rotator cuff. Their main conclusion was that the (Ecc/IR: Conn/ER) ratio of the injured to the noninjured shoulder was lower (IR:ER) (1.84:1.71) on the left side than on the right side (IR:ER) (1.97:1.69). The authors recommended strengthening the internal rotator cuff to prevent injury. The nature of overhead sports requires the player’s dominant arm to generate higher strength values of the IR for execution of the sporting motion. Increased IR strength values leading to different ER:IR ratios were determined in handball players [ 51 , 60 ]. Therefore, functional ratios lower than the ER:IR (1.00:1.00) ratio recommended in the literature have been observed [ 51 , 58 ]. It is suggested that eccentric external rotation (eccER) should be stronger than concentric internal rotation (connIR) to compensate for the deceleration and control of the glenohumeral head (GH) in the throwing motion in overhead sports. Numerous authors of the included primary studies agree that a higher ER:IR strength ratio prevents the development of shoulder dysfunction [ 50 – 51 , 58 , 60 , 108 ]. . A decrease in the subacromial space (SAS) was observed in the presence of a stronger IR. A stronger IR resulted in a decreased ER:IR agonistic-antagonistic force couple ratio. A decreased SAS leads to impingement of the rotator cuff (RC) in the abduction motion from 0° to 60° [ 47 ]. This decreased ER:IR ratio had a knock-on effect on destabilizing the dynamic control of the humeral head on the glenoid in overhead sports, such as softball, leading to SIS [ 47 ]. . Regardless of the shoulder motion required or strength of evidence provided, strengthening and restoring the ER:IR force couple to a better strength ratio is deemed advisable for improved shoulder stability in both athletes and members of the general population. 8.4 IR ROM Decreased internal rotation has been identified as a precursor to developing shoulder dysfunction by various authors of the included primary studies pooled into a meta-analysis (4) (Fig. 9 ) [ 53 , 72 , 77 – 78 ]. Populations included overhead sports such as cricket, handball and tennis, as well as members of the general population [ 48 ]. IR must not be measured in isolation; however, ER and TROM should be measured and considered at the same time. In overhead sports, particularly baseball, a symmetrical loss of IR is often offset by a symmetrical gain in ER ROM [ 74 ]. It was noted that the presence of IR ROM was less pronounced, even though still present, in a sample of the general public than in sporting populations, such as in overhead sports, tennis, handball, cricket, swimming, and underhand sports (rugby) [37,48,72,78 − 77] (Table 9). Several studies have shown that players complaining of shoulder pain from posterosuperior internal impingement present with decreased IR and ER and a decreased total arch of movement (TAM) [ 77 , 72 ]. With an overall side-to-side comparison of the included primary studies of the present SR, a general decrease in TROM was determined, which indicated that both ER and IR decreased. This was also found in populations such as tennis, cricket, handball, swimming and underhand (rugby) [ 37 , 58 , 72 , 77 ] and in members of the general public [ 48 ]. This phenomenon was not observed for baseball players [ 110 – 111 ]. It can therefore be surmised that decreased IR and increased ER might be more common in subdisciplines such as baseball, where extremely high velocities are generated in the overhead throwing motion, potentially leading to compensatory imbalance between the ER and the IR. 8.5 GIRD GIRD has been linked to an increased risk of developing shoulder dysfunction by several of the authors of the included primary studies of the present systematic review in overhead sports such as tennis and handball at a professional level [72,78 − 77]. The pooled results are summarized in the meta-analysis (5) (Fig. 11 ). Even though not covered in the present systematic review, when considering limited IR, osseous adaptation should also be considered a contributing factor to the limitation of IR. This approach is especially applicable in overhead sports, such as baseball [ 74 ]. Reuther [ 74 ] observed that if humeral retroversion is corrected in the presence of the measured GIRD, the GIRD disappears; thus, soft tissue changes are not solely responsible for the GIRD. Lubiatowski [ 77 ] reported that a greater incidence of shoulder pain was present in patients with internal deficits of more than 20 degrees. A GIRD of up to 41 degrees has been determined in the symptomatic shoulders of individuals in a general population group [ 112 ]. A greater incidence of internal impingement was present when both internal deficits of more than 25 degrees and a total arch of motion of more than 20 degrees coexisted [ 77 ]. Total arch of motion deficits (TAMDs) of between 6 degrees to 16.7 have been found in pathological shoulders [ 77 , 78 ] (Online Resource 1). This is more than the 5-degree results obtained in the original study proposed by Wilk [ 111 ]. The overall conclusions reached in the study of skilled amateur tennis players were that GIRD, posterior capsule tightness, external rotation strength deficits and ERG were present in combination in the clinical presence of internal impingement and the superior labral anterior posterior region. Compared with those in the controls, (SLAP) lesions existed in the symptomatic dominant arm of the players [ 53 ]. Posterosuperior internal impingement was associated with decreased IR, ER and TAM, as well as greater TAMD and GIRD, in tennis players with pain than in tennis players without pain in their primary study [ 53 ]. Additionally, GIRD has been associated with posterior capsule thickening and stiffness as well as internal impingement. 8.6 Posterior capsule Structures that can cause a decrease in IR are the posterior inferior cuff (infraspinatus and teres minor) and the posterior capsule [ 19 , 113 – 114 ]. Posteroinferior shortening of the abovementioned structures results in a posterosuperior shift of the humerus, causing internal impingement [ 19 , 115 ]. This phenomenon can potentially maximize the peel-back forces of the long head of the biceps and predispose an athlete to developing SLAP lesions [ 19 , 116 ]. GIRD not only occurs in baseball players, as originally described by Pappas [ 114 ] and Burkhart [ 117 ] but also occurs in other overhead disciples, such as skilled amateur tennis players [ 53 , 113 ], handball players [ 77 ] and cricket players [ 57 ]. 8.7 ER gain Partial rotator cuff tears (RCTs) were accompanied by greater ER and total arch of movement gain (TAMG) in a study of professional handball players [ 77 ]. The findings are described in detail in the online supplement (Online Resource I). No difference was observed in either ROM or strength during the preseason on gymnasts between athletes sustaining an injury and injury-free athletes [ 54 ]. The bilateral nature of the sport may provide a link to the lack of observed differences [ 54 ]. 8.8 Pectoralis minor Shortening of the pectoralis minor has been identified as contributing to scapula dyskinesis [ 21 , 96 , 119 ]. The results of the primary studies included in the current systematic review revealed that a shortened PMm can cause anterior tilt, protraction and internal rotation of the scapula [ 99 , 119 ]. This places the scapular stabilizing muscles, particularly the lower fibers of the trapezius and the serratus anterior lower fibers, in a biomechanically altered position with reduced posterior tilt of the scapula [ 99 ]. Decreased flexibility of the PMm and ER was noted after a bout of swimming in the painful group of swimmers [ 64 ]. Increased PMm activity occurred in a painful group of participants who presented with SIS in a laboratory-controlled group [ 84 ]. Decreased IR and ER decreased the flexibility of the PMm and the posterior capsule, as did [ 57 ], which determined the weakness of the SA in their study of cricket players. Decreased flexibility of the PMm was observed in wheelchair users [ 67 ]. Decreased flexibility of the pectoralis minor and the latissimus dorsi was associated with an increase in pain in competitive swimmers [ 119 ]. The presence of scapular dyskinesis has also been observed with alterations in the PMm using different measurement methods [ 30 , 44 , 85 – 90 , 120 ]. See (SoF) (Online Resource I) and Table of Characteristics (Online Resource 2). 8.9 Scapular dyskinesis Numerous authors have investigated the presence of scapular dyskinesis and its relevance [ 46 , 61 , 76 , 121 – 123 ] in both athletic and nonathletic population groups. Heterogeneity within the measurement properties used for scapular kinematics prevented pooling of studies. The SWiM approach was used, and the results of the identified studies are summarized in the Table of Characteristics (Online Resource 2) [ 41 ]. In their text and opinion study, Saini [ 122 ] highlighted the importance of the early identification and correction of observed scapular dyskinesis in tennis players. The control and position of the scapula are dependent mainly on scapular stabilizers due to an inherent lack of bony stability. Therefore, the abovementioned imbalance in the scapular stabilizers of the included studies may be clinically relevant. Phadke [ 123 ] concluded that decreased strength of the lower trapezius leads to less upward rotation of the scapula. Huang [ 76 ] observed increased upper trapezius activity in the presence of scapular inferior angle prominence in symptomatic shoulders. Moreover, Kolber [ 46 ] reported the presence of increased strength of the upper trapezius in weightlifters with subacromial impingement (SIS). Borstad and Ludwig [ 121 ] investigated scapular kinematics with a motion sensor (Fastrak) and concluded that less upward rotation was present at lower angles and more anterior tipping of the scapula was present at greater angles of elevation in symptomatic shoulders. The positioning of the scapula is mainly controlled by scapular stabilizers and imbalances in muscle strength, and more important force couples in these muscles may lead to abnormal positioning of the scapula, which has a negative impact on the functioning of the glenohumeral joint. The previously mentioned imbalances in scapular stabilizers, as highlighted by various researchers, can hence lead to scapular dyskinesis or dyskinesia. However, an interesting observation of decreased muscle strength of the rotator cuff was made by [ 61 ]. According to the authors, this was a more frequent finding than the presence of scapular dyskinesis and limitation of active range of motion in painful shoulders. 9 Conclusion The present systematic review identified seven modifiable musculoskeletal factors among both athletic and nonathletic population groups. Decreased ER strength, a decreased ER:IR strength ratio, decreased IR, GIRD, ER gain, PMm shortness and scapular dyskinesis were associated with shoulder dysfunction. Modifiable musculoskeletal factors synthesized into several meta-analyses provided strong evidence for the presence of decreased ER strength, decreased ER:IR strength force couple ratios, decreased IR and GIRD being associated with shoulder dysfunction. Weaker evidence for the presence of a shortened PMm and scapular dyskinesis in the presence of shoulder dysfunction was determined. Regardless of the level of evidence, the presence of the abovementioned modifiable musculoskeletal factors was determined to be associated with shoulder dysfunction. Recommendations : The etiology of shoulder dysfunction is multifactorial and complex in nature. Early identification and correction of identified altered modifiable musculoskeletal factors have been shown to prevent the development of shoulder dysfunction in the current literature. All the identified modifiable musculoskeletal factors of the present systematic review should be considered in the comprehensive assessment and rehabilitation of the shoulder joint. Moreover, correcting for the identified modifiable musculoskeletal factors, normalizing all the affected force–couple ratios of the modifiable musculoskeletal factors and increasing the flexibility of identified modifiable musculoskeletal factors should lead to improved biomechanics of the scapulohumeral complex. This phenomenon is thought to be key in the rehabilitation process and should be monitored in all populations and not only in the athletic population. Early identification of biomechanical dysfunctions associated with any particular movement pattern of the shoulder can aid in preventing the development of shoulder pathology. A new evaluation model incorporating all the abovementioned modifiable musculoskeletal factors is therefore proposed. Limitations : However, additional primary longitudinal studies should be conducted on the association between modifiable risk factors and the development of shoulder dysfunction. Due to the heterogeneity of the included primary studies, only a few studies reporting on the RR and OR could be pooled into a meta-analysis. Not all the included primary observational studies reported on RRs and ORs, and additional research in this area is needed. No data could be found on the role of the latissimus dorsi or the subscapularis in either primary observational or longitudinal studies or on the risk of developing shoulder dysfunction. However, even though the methodological quality of the studies included in this review was fair overall, namely, at levels 3 and 4, meaningful information was collected. Declarations Competing Interest: All the authors certify that they have no affiliations with or involvement in any organization or entity with any financial interest or nonfinancial interest in the subject matter or materials discussed in this manuscript. Funding: No funds, grants, or other support was received. Availability of data: The authors declare that the data supporting the findings of this study are available within the paper and in the supplementary online information files. 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EFORT open reviews 4(1):25–32 Burkhart SS, Morgan C (2001) SLAP lesions in the overhead athlete. Orthop Clin 32(3):431–441 Colby LY, Borstad JO, Kisner CA (2017) Improved Mobility. Therapeutic Exercise: Found Techniques. ;82 Tate A, Turner GN, Knab SE, Jorgensen C, Strittmatter A, Michener LA (2012) Risk factors associated with shoulder pain and disability across the lifespan of competitive swimmers. J Athl Train 47(2):149–158 Lee JH, Park JS, Park HJ, Ryoo HJ, Jeong WK (2022) Are Rotator Muscle Performance and Posterior Shoulder Capsule Tightness Related to Glenohumeral Internal Rotation Deficit in Male College Baseball Players? Clin Orthop Surg 14(4):576 Borstad JD, Ludewig PM (2002) Comparison of scapular kinematics between elevation and lowering of the arm in the scapular plane. Clin Biomech Elsevier Ltd 17(9–10):650–659 Saini SS, Shah SS, Curtis AS (2020) Scapular dyskinesis and the kinetic chain: recognizing dysfunction and treating injury in the tennis athlete. Curr Rev Musculoskelet Med 13:748–756 Phadke V, Camargo P, Ludewig P (2009) Scapular and rotator cuff muscle activity during arm elevation: A review of normal function and alterations with shoulder impingement. Rev Bras Fisioter 13(1):1–9 PMID: 20411160; PMCID: PMC2857390 Additional Declarations The authors declare no competing interests. Supplementary Files Appendices.docx Cite Share Download PDF Status: Posted Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-4555953","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Systematic Review","associatedPublications":[],"authors":[{"id":312469558,"identity":"94534d5e-a2eb-487c-9745-3690c9ecce4f","order_by":0,"name":"Sonia Briel","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA40lEQVRIiWNgGAWjYJCCAwwVDDwMEkBWAvFazpCqhYGxDUhIEKtavr334IGf87bJmEv3GH94UMEgz8/A/vADPi0GZ84lHOzddpvHcs4ZM4mEMwyGMxsYkvHaaCCRY3CAF6jF4EaOGUNiG0OCwQGGA3i1yM/IMTj4dw5Yi/EHiBbG5h94PXMjx+AwbwNYi4EERAszG36HnTljcFjmGNAvM9LKgH6RMJzZzMZmgddh7T3GH9/U3LY3l0je/PFHhY08P3v74xt4HQa3joHDgAEcO8xEqQdrYX9ArNpRMApGwSgYYQAA2YJJisoUBvgAAAAASUVORK5CYII=","orcid":"https://orcid.org/0000-0002-8445-6528","institution":"University of the Witatersrand","correspondingAuthor":true,"submittingAuthor":false,"prefix":"","firstName":"Sonia","middleName":"","lastName":"Briel","suffix":""},{"id":312472889,"identity":"1fc3f873-45bc-4b10-9c57-d134f2c9da5d","order_by":1,"name":"Corlia Brandt","email":"","orcid":"https://orcid.org/0000-0002-8445-1348","institution":"University of the Witwatersrand","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Corlia","middleName":"","lastName":"Brandt","suffix":""},{"id":312473504,"identity":"c835dc45-7f9e-44ad-ab22-6dd3543cf9c6","order_by":2,"name":"Benita Oliver","email":"","orcid":"https://orcid.org/0000-0001-9287-8301","institution":"Oxford Brookes Univerity","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Benita","middleName":"","lastName":"Oliver","suffix":""},{"id":312476871,"identity":"a70bc4fa-d45a-4b5a-bd76-5c79eda162fd","order_by":3,"name":"Franso-Mari Olivier","email":"","orcid":"https://orcid.org/0000-0001-9470-6087","institution":"University of the Witwatersrand","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Franso-Mari","middleName":"","lastName":"Olivier","suffix":""}],"badges":[],"createdAt":"2024-06-10 05:40:59","currentVersionCode":1,"declarations":{"humanSubjects":false,"vertebrateSubjects":false,"conflictsOfInterestStatement":false,"humanSubjectEthicalGuidelines":false,"humanSubjectConsent":false,"humanSubjectClinicalTrial":false,"humanSubjectCaseReport":false,"vertebrateSubjectEthicalGuidelines":false,"coiExplicitlySet":false},"doi":"10.21203/rs.3.rs-4555953/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-4555953/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":58152606,"identity":"9cf052b2-c1bc-47e9-ab97-12548ac8f94f","added_by":"auto","created_at":"2024-06-11 20:23:01","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":135161,"visible":true,"origin":"","legend":"\u003cp\u003ePRISMA flowchart of the included studies. From: Page MJ, McKenzie JE, Bossuyt PM, Boutron I, Hoffmann TC, Mulrow CD, et al. The PRISMA 2020 statement: an updated guideline for reporting systematic reviews. BMJ 2021;372: n71. doi:\u003c/p\u003e\n\u003cp\u003e10.1136/bmj. n71. For more information, visit:\u003ca href=\"http://www.prisma-statement.org/\"\u003e \u003c/a\u003e\u003ca href=\"http://www.prisma-statement.org/\"\u003ehttp://www.prisma\u003c/a\u003e\u003ca href=\"http://www.prisma-statement.org/\"\u003e-\u003c/a\u003e\u003ca href=\"http://www.prisma-statement.org/\"\u003estatement.org/\u003c/a\u003e\u003ca href=\"http://www.prisma-statement.org/\"\u003e\u0026nbsp;\u003c/a\u003e\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-4555953/v1/e0e169e33774d88e0541433f.png"},{"id":58152121,"identity":"6f4c25fb-0cad-4051-bc1f-85ac4974bcef","added_by":"auto","created_at":"2024-06-11 20:15:01","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":774300,"visible":true,"origin":"","legend":"\u003cp\u003eA global representation of the geographical location of the primary studies included in the current systematic review.\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-4555953/v1/ae8aba77f3df6df9b149df90.png"},{"id":58153718,"identity":"89723f10-f5d8-4a89-b558-3c434dd5ea34","added_by":"auto","created_at":"2024-06-11 20:31:01","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":146940,"visible":true,"origin":"","legend":"\u003cp\u003ePopulations and participants of the included studies in the present systematic review.\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-4555953/v1/01a7cc4cbbeef825f318bf7b.png"},{"id":58152119,"identity":"76c1cc81-676a-4a8b-ae06-7d2cb8c541d2","added_by":"auto","created_at":"2024-06-11 20:15:01","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":40182,"visible":true,"origin":"","legend":"\u003cp\u003eMeta-analysis (1): The risk ratios for the associations with IR ROM were calculated forthe included primary studies.\u003c/p\u003e","description":"","filename":"4.png","url":"https://assets-eu.researchsquare.com/files/rs-4555953/v1/86a223bedd4da03ac60c3e5f.png"},{"id":58152620,"identity":"7aea7676-1dba-402e-aaf9-4e685754d74c","added_by":"auto","created_at":"2024-06-11 20:23:01","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":141104,"visible":true,"origin":"","legend":"\u003cp\u003eMeta-analysis (3) of isometric and isokinetic strength in the ER between the cases and the controls.\u003c/p\u003e","description":"","filename":"5.png","url":"https://assets-eu.researchsquare.com/files/rs-4555953/v1/a109684649da7cf307c1b35a.png"},{"id":58153717,"identity":"ce3cbeb8-a545-4ba9-b2b9-4323c3083369","added_by":"auto","created_at":"2024-06-11 20:31:01","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":68008,"visible":true,"origin":"","legend":"\u003cp\u003eSensitivity analysis was conducted to reduceheterogeneity.\u003c/p\u003e","description":"","filename":"6.png","url":"https://assets-eu.researchsquare.com/files/rs-4555953/v1/2052bb14558262e7035a8926.png"},{"id":58152115,"identity":"bb007119-630b-45fa-91d9-c8252369bba9","added_by":"auto","created_at":"2024-06-11 20:15:01","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":31351,"visible":true,"origin":"","legend":"\u003cp\u003eNo publication bias was detected in the funnel plot generated from the isometric and isotonic strength values between the cases and the controls.\u003c/p\u003e","description":"","filename":"7.png","url":"https://assets-eu.researchsquare.com/files/rs-4555953/v1/eef096f28fd19ad58dd47b53.png"},{"id":58152124,"identity":"8be36078-411f-4376-9d49-5bfa361f076d","added_by":"auto","created_at":"2024-06-11 20:15:01","extension":"png","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":71348,"visible":true,"origin":"","legend":"\u003cp\u003eMeta-analysis (3) depicting the ER:IR strength ratios between the cases and the controls.\u003c/p\u003e","description":"","filename":"8.png","url":"https://assets-eu.researchsquare.com/files/rs-4555953/v1/6d0f91eb7185641b6740b38e.png"},{"id":58152623,"identity":"1e2ad575-8b73-49fe-94b8-5142984d7c7c","added_by":"auto","created_at":"2024-06-11 20:23:01","extension":"png","order_by":9,"title":"Figure 9","display":"","copyAsset":false,"role":"figure","size":119057,"visible":true,"origin":"","legend":"\u003cp\u003eMeta-analysis of IR between the cases and the controls for IR ROM.\u003c/p\u003e","description":"","filename":"9.png","url":"https://assets-eu.researchsquare.com/files/rs-4555953/v1/978847dba0b88967b80845e4.png"},{"id":58152126,"identity":"400aba37-bfbf-4c19-a09e-311f7f283bff","added_by":"auto","created_at":"2024-06-11 20:15:01","extension":"png","order_by":10,"title":"Figure 10","display":"","copyAsset":false,"role":"figure","size":76510,"visible":true,"origin":"","legend":"\u003cp\u003eSensitivity analysis for reducing heterogeneity in IR ROM.\u003c/p\u003e","description":"","filename":"10.png","url":"https://assets-eu.researchsquare.com/files/rs-4555953/v1/3aa037a577ed01788e3b3838.png"},{"id":58154357,"identity":"d52e2c9b-ddf7-4fef-9f03-fafc27f0a6f3","added_by":"auto","created_at":"2024-06-11 20:39:01","extension":"png","order_by":11,"title":"Figure 11","display":"","copyAsset":false,"role":"figure","size":76706,"visible":true,"origin":"","legend":"\u003cp\u003eMeta-analysis (5): Forest plot depicting the mean difference in GIRD between the cases and the controls.\u003c/p\u003e","description":"","filename":"11.png","url":"https://assets-eu.researchsquare.com/files/rs-4555953/v1/d07b211e1ebda43d96cde5c4.png"},{"id":58155361,"identity":"05584b81-7567-40f7-ad34-689de7c907d1","added_by":"auto","created_at":"2024-06-11 20:47:02","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":2555605,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-4555953/v1/0d2b93f8-c35c-4af4-9c0e-733d6c9b3f11.pdf"},{"id":58152118,"identity":"72b40659-2be0-4593-94be-69d0f13d3f09","added_by":"auto","created_at":"2024-06-11 20:15:01","extension":"docx","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":64399,"visible":true,"origin":"","legend":"","description":"","filename":"Appendices.docx","url":"https://assets-eu.researchsquare.com/files/rs-4555953/v1/7e8d46eb41c7dad531bcd15f.docx"}],"financialInterests":"The authors declare no competing interests.","formattedTitle":"\u003cp\u003eModifiable musculoskeletal factors and their association with shoulder function in adults: A systematic review of risk and association\u003c/p\u003e","fulltext":[{"header":"Key Points","content":"\u003cp\u003eDecreased external rotation strength, decreased external versus internal rotation strength ratios, decreased internal rotation and GIRD predispose a shoulder to dysfunction.\u003c/p\u003e\n\u003cp\u003eAll musculoskeletal factors identified with this systematic review should be addressed at one point in time during both the evaluation and rehabilitation process.\u003c/p\u003e"},{"header":"1. Introduction","content":"\u003cp\u003eShoulder pain affects 16\u0026ndash;21% of the general population [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e, \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]. In addition to being highly prevalent, shoulder pathology is potentially a debilitating and challenging diagnosis [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e]. Various researchers have concluded that the rotator cuff is responsible for shoulder pain among patients [\u003cspan additionalcitationids=\"CR5\" citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e]. In their study of imaging pathology, the rotator cuff was concluded to be the main pain driver in shoulder pain, determined to be as high as 50% on ultrasound imagery and 65% on magnetic resonance arthrogram [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e]. The pathogenesis of rotator cuff injuries (RCIs) is multifactorial and controversial, but the shape of the acromion is still thought to be a contributing factor to the development of shoulder pain [\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e]. The confirmed findings that tears of the supraspinatus muscle are located mainly within the tendon or on the articular side of the joint contradict the acromial impingement syndrome model [\u003cspan additionalcitationids=\"CR9\" citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eThe force coupling mechanism of rotator cuffs can be disrupted by weakening or injury to the rotator cuff muscles [\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e, \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e]. This destabilization of the humeral head on the glenoid cavity occurs when the muscle length and force are abnormal therefore, arthrokinematics are disrupted [\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e, \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e]. Abboud and Soslowsky [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e] concluded that altered force couple vectors of the rotator cuff can lead to instability and thus destabilization of the humeral head on the glenoid cavity. An imbalance in this muscular system might be conducive to the development of structural damage in the glenohumeral joint [\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eThe supraspinatus is the first muscle to activate during elevation [\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e]. The compressive force provided by the supraspinatus contributes to the stability of the humeral head in the glenoid cavity [\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e]. In their electromyography (EMG) study, Abboud and Soslowsky [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e] reported that from 60\u0026deg; to 150\u0026deg; in the abduction plane of movement, contractions of both the subscapularis and the infraspinatus occurred. The subscapularis muscle not only functions as a humeral head depressor but also stabilizes the humeral head and functions as an internal rotator of the humeral head [\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e, \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eAdditionally, other specific musculoskeletal factors (shortening and tightness of the posterior capsule, pectoralis minor, latissimus dorsi, short head of the biceps and subscapularis) have been independently identified by various researchers as contributing factors to the development of shoulder pain [\u003cspan additionalcitationids=\"CR20\" citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e]. The anatomical attachment of the short head of the biceps brachii to the anterior tip of the coracoid process can contribute to scapular dyskinesis [\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e].\u003c/p\u003e \u003cp\u003ePosterior capsule tightness and a decreased range of motion (ROM), specifically the internal range (IR) of motion, have been associated with an increased incidence of shoulder pain [\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e]. Shortening and hypertrophy of the posterior capsule have been associated with decreased internal rotation and resultant anterior migration of the humeral head [\u003cspan additionalcitationids=\"CR25\" citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e]. Factors contributing to the development of glenohumeral joint internal rotation deficit (GIRD) include posterior capsule tightness and stiffness of the posterior muscle tendon unit [\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e].\u003c/p\u003e \u003cp\u003e A preliminary search of the JBI Evidence Synthesis, Cochrane Database of Systematic Reviews, MEDLINE (PubMed), and PROSPERO databases was conducted using the following search terms: rotator cuff, shoulder, scapulothoracic joint, musculoskeletal, GIRD, and subacromial impingement syndrome (SIS). To the best of our knowledge, only two systematic reviews were conducted that identified potential risk factors predictive of shoulder pain Hill [\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e] conducted one and the other was by Keller [\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e]. In their systematic review, Hill [\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e] explored risk factors such as GIRD, internal and external rotation strength of the rotator cuff and clinical instability leading to shoulder pain in a subpopulation of swimmers. In their systematic review with meta-analysis, the authors investigated only GIRD and increased external rotational gain as risk factors favoring injuries in a subpopulation of overhead athletes [\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e]. In their study on volleyball players, Reeser [\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e] stated that an understanding of modifiable risk factors is essential for preventing shoulder pain and providing optimal care for players presenting with shoulder pain.\u003c/p\u003e \u003cp\u003eLewis [\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e] concluded that considerable deficits still exist in our current understanding of rotator cuff-related shoulder pain (RCRSP). These include (1) the exact origin of symptoms, (2) the determination of more accurate diagnostic labels, (3) better epidemiological studies of symptomatic shoulder pain patients, (4) more accurate establishment of symptomatic tissues to target treatment, and (5) determination of the best treatment modalities for symptomatic shoulder pain patients [\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e]. His main conclusion was that there is a need for ongoing research to seek a better understanding of the underlying etiology, better assessment models and the development of better management protocols [\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e]. There is a need for clarification and a better understanding of the influence of musculoskeletal factors and their association with shoulder function. The current models used in the diagnosis of shoulder dysfunction might thus be outdated and not appropriate or applicable in clinical practice.\u003c/p\u003e \u003cp\u003eThe overall aim of this systematic review was to determine modifiable musculoskeletal factors and their associations with shoulder function in adults aged between 18 and 75 years. The purpose of this review was ultimately to identify a cluster of musculoskeletal tests to determine the risk factors associated with shoulder dysfunction.\u003c/p\u003e"},{"header":"2. Methodology","content":"\u003cp\u003eThis systematic review was conducted in accordance with the JBI methodology for Systematic Reviews of Etiology and Risk [\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e].\u003c/p\u003e \u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003e2.1 Inclusion criteria\u003c/h2\u003e \u003cdiv id=\"Sec4\" class=\"Section3\"\u003e \u003ch2\u003e2.1.1 Participants\u003c/h2\u003e \u003cp\u003eStudies including females and males globally with and without shoulder dysfunction aged between 18 and 75 years were included in this review. Studies on participants from both the general population and the athletic population were included (athletic subgroups could be classified as any sporting fraternity, e.g., overhead sport, tennis, cricket or underhand such as rugby). Studies involving participants with postoperative shoulder dysfunction were not included.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec5\" class=\"Section3\"\u003e \u003ch2\u003e2.1.2 Exposure of interest\u003c/h2\u003e \u003cp\u003eStudies that investigated modifiable musculoskeletal factors impacting the biomechanical and arthrokinematical functioning of the shoulder joint, as independent variables, were explored and included in the study. Only modifiable musculoskeletal factors were included, which were defined as the musculoskeletal and capsular factors listed below; therefore, factors such as bony factors were excluded. The following modifiable musculoskeletal factors were included:\u003c/p\u003e \u003cp\u003e \u003col\u003e \u003cspan\u003e \u003cli\u003e \u003cp\u003ePectoralis minor, latissimus dorsi and rotator cuff (supraspinatus, infraspinatus, teres minor, and subscapularis) muscle lengths were measured with a caliper, goniometer or tape measure.\u003c/p\u003e \u003c/li\u003e \u003c/span\u003e \u003cspan\u003e \u003cli\u003e \u003cp\u003eThe strength of the pectoralis minor, latissimus dorsi, and rotator cuff (supraspinatus, infraspinatus, teres minor, and subscapularis) muscles was measured with a dynamometer, and the results included derived measurements such as balance/imbalance of strength ratios of the rotator cuff, e.g., expressed as ratios of internal/external versus external/internal rotators;\u003c/p\u003e \u003c/li\u003e \u003c/span\u003e \u003cspan\u003e \u003cli\u003e \u003cp\u003eCapsular flexibility, such as anterior and posterior capsule length measured using a goniometer or inclinometer;\u003c/p\u003e \u003c/li\u003e \u003c/span\u003e \u003cspan\u003e \u003cli\u003e \u003cp\u003eThe shoulder range of movement was measured using a goniometer or inclinometer.\u003c/p\u003e \u003c/li\u003e \u003c/span\u003e \u003c/ol\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec6\" class=\"Section3\"\u003e \u003ch2\u003e2.1.3 Outcome\u003c/h2\u003e \u003cp\u003eThe outcome of interest was shoulder dysfunction. Shoulder dysfunction, the dependent variable, included any one or a combination of the following: the presence of discomfort, measured with subjective patient self-reports; pain, measured and reported on the visual analog scale (VAS) or on the numeric pain rating scale (NPRS); or dyskinesis, measured though kinematic analysis. Shoulder dysfunction was also reported with outcome measurement questionnaires such as but not limited to the Shoulder Pain and Disability Index (SPADI).\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec7\" class=\"Section3\"\u003e \u003ch2\u003e2.1.4 Type of study\u003c/h2\u003e \u003cp\u003eBoth observational (cross-sectional, case‒control, prospective and retrospective and longitudinal cohort studies; case series and case reports), analytical and descriptive studies were included in this review. Experimental and randomized control trials were excluded from the study because only the association of dysfunction of the shoulder joint with modifiable musculoskeletal factors was established.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec8\" class=\"Section3\"\u003e \u003ch2\u003e2.1.5 Search strategy\u003c/h2\u003e \u003cp\u003eThe methodology and meta-analysis process, as detailed in the JBI Reviewer\u0026rsquo;s Manual for Etiology and Risk [\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e], were followed, and the guidelines proposed by the PRISMA (Preferred Items for Systematic Reviews and Meta-Analysis) statement [\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e] were followed. The Population, Problem, Intervention, Comparison or Control, and Outcome (PICO) methodology [\u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e35\u003c/span\u003e] was adapted to fit the study design of our systematic review to Population, Etiology, and Outcome (PEO). The research question and, subsequently, search terms were developed around the PEO concept. The search strategy included both published and unpublished studies. A three-step approach was followed. First, an initial limited search of PubMed Central and CINAHL (EBSCOhost) was undertaken to identify articles on the topic. The text words used were from the titles and abstracts of relevant articles, and the index terms used to describe the articles were used to develop a full search strategy for PubMed Central (Appendix I). Second, for the main review, all identified keywords were explored using both MeSH and text words and were appropriately adapted for each database. Third, all the reference lists of all the studies selected for critical appraisal (backward citation tracking) were screened for additional studies. Forward citation tracking using Google Scholar and Academia.edu was then performed for the identified studies. No restriction was placed on language, but the age was limited to adults aged eighteen years and older. Studies published in all languages were included. An in-depth search across twelve databases was conducted from inception to the end of March 2023, and the relevant articles were included. An updated search was conducted from the beginning of April 2023 to the 6th of March 2024, and the applicable articles were imported. The databases searched included PubMed (Advanced), MEDLINE, MEDLINE COMPLETE, Masterfile, and SPORTDiscus via EBSCOhost; the Cumulative Index to Nursing and Allied Health Literature (CINAHL); the Physiotherapy Evidence Database (PEDro); and the Web of Science and Scopus (Elsevier). The information sources of unpublished and gray literature included Open Gray, Gray Matter, and MasterFile Premier (EBSCO) (Appendix I). All the included and excluded studies are depicted by means of the PRISMA flowchart (Figure I) [\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e].\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec9\" class=\"Section3\"\u003e \u003ch2\u003e2.1.6 Study selection\u003c/h2\u003e \u003cp\u003eFollowing the search, all identified citations were collated and uploaded into EndNote X9.3.3 (Clarivate Analytics, PA, USA) (2021), after which duplicates were removed. Potentially relevant studies were retrieved in full, and their citation details were imported into the JBI System for the Unified Management, Assessment, and Review of Information (JBI SUMARI) [\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e]. Titles and abstracts of the uploaded articles were subsequently reviewed by two independent reviewers for assessment against the inclusion criteria of the review.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec10\" class=\"Section3\"\u003e \u003ch2\u003e2.1.7 Data extraction\u003c/h2\u003e \u003cp\u003eAll studies, regardless of the results of their methodological quality, underwent data extraction, and some were synthesized into meta-analyses. Data were extracted from the studies included in the review by two independent reviewers using standardized JBI SUMARI data extraction tools [\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e]. The extracted data included specific details about the population (participant characteristics, age, sport discipline or sedentary), study methods, aim, context, exposure of interest, study setting and location (country), and outcomes of significance to the review question (Table of Characteristics-Online Resource 2 and Figs.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e, \u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e). No disagreements arose that required the intervention of the third reviewer.\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e"},{"header":"3. Assessment of Methodological Quality","content":"\u003cp\u003eEligible studies were critically appraised by two independent reviewers (SB and FM-O) at the study level for methodological quality in the review using standardized critical appraisal instruments from the JBI [\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e]. The numerical scores for the analytical cross-sectional studies were scores out of eight and those for the eligible cohort studies out of eleven (\u003cspan refid=\"Sec41\" class=\"InternalRef\"\u003eAppendix 3\u003c/span\u003e). Methodological quality was deemed high overall for the included studies included in the meta-analyses and for both the eligible analytical cross-sectional and the eligible cohort studies. Two studies, Skazalski [\u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e] and Peckitt [\u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e37\u003c/span\u003e], were of lower methodological quality because they did not state how confounding factors were dealt with (\u003cspan refid=\"Sec41\" class=\"InternalRef\"\u003eAppendix 3\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eMethodological quality was documented throughout the appraisal process. All studies, regardless of their methodological quality, underwent data extraction, and some studies were synthesized and combined into meta-analyses (Figs.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e, \u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e, \u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003e, \u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e9\u003c/span\u003e, \u003cspan refid=\"Fig11\" class=\"InternalRef\"\u003e11\u003c/span\u003e). All the data used for generating the meta-analyses were taken from both the eligible analytical cross-sectional and eligible cohort studies. The data were subjected to double entry by two reviewers (SB and FM-O). The results of the critical appraisal were reported in tabular format with accompanying narratives highlighting the main findings of individual studies (Online Resource 1) and in the Table of Characteristics (Online Resource 2).\u003c/p\u003e"},{"header":"4 Data synthesis","content":"\u003cp\u003eClinical, methodological, and statistical heterogeneity was determined [\u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e38\u003c/span\u003e]. Risk ratio (RR) and odds ratio (OR) data were extracted from the primary longitudinal studies included (Table I), answering the proposed study questions concerning the risk of shoulder dysfunction in the present systematic review. When the RR was unavailable, it was calculated using the SPSS Statistics 28.01.1.1 (15) IBM Corp., Armonk, NY, USA) package, and the results obtained were imported into JBI SUMARI for the generation of a meta-analysis (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e). Studies that reported the mean and standard deviation of the identified primary studies reporting on the cases and on the controls were included in the proposed meta-analysis (Figs.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e, \u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e, \u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003e, \u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e9\u003c/span\u003e, \u003cspan refid=\"Fig11\" class=\"InternalRef\"\u003e11\u003c/span\u003e). The effect size was calculated to measure the strength of association between the groups of the identified studies and was expressed as the standardized mean difference (SMD) for continuous data for all groups. The 95% confidence intervals were calculated for the analysis. Study data were pooled in statistical meta-analyses using the JBI SUMARI to increase the accuracy of the derived overall effect size [\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e]. Cohen\u0026rsquo;s d method was employed to estimate the pooled SMD and weight using an inverse variance method [\u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e39\u003c/span\u003e]. Due to the inherent suspected heterogeneity across studies, a random effects model (using the DerSimonian and Laird method) was used to estimate the RR and the SMD.\u003c/p\u003e \u003cp\u003eFive comparative meta-analyses were composed using the JBI SUMARI [\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e]. The effect sizes (RR) and (OR) were extracted to determine the association between shoulder dysfunction and modifiable musculoskeletal factors (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e). Meta-analysis (1): The risk ratio between musculoskeletal modifiable risk factors and internal rotation (IR) and the development of shoulder dysfunction.\u003c/p\u003e \u003cp\u003eThe effect size expressed as the standardized mean difference (SMD) was used in the etiology meta-analyses (Meta-analysis 2\u0026ndash;5).\u003c/p\u003e \u003cp\u003eMeta-analysis (2): Studies that reported on the external rotation strength of the cases and the controls measured using either a handheld dynamometer with isometric testing or isokinetic dynamometry with isokinetic testing were selected.\u003c/p\u003e \u003cp\u003eMeta-analysis (3): Studies reporting on the strength ratio of the external rotators (ERs): internal rotators (IRs) of the cases and the controls were included.\u003c/p\u003e \u003cp\u003eMeta-analysis (4): Studies reporting on the internal range of movement) measured using an inclinometer in degrees of the cases and the controls were included in the analysis.\u003c/p\u003e \u003cp\u003eMeta-analysis (5): Studies reporting on the GIRD of the cases and the controls were included in the analysis.\u003c/p\u003e \u003cp\u003eHeterogeneity within the meta-analysis of the results was statistically tested using the I\u003csup\u003e2\u003c/sup\u003e test. Sensitivity analysis was also conducted to explore the impact of the included and excluded studies on the heterogeneity of the meta-analyses. The pooled results of the meta-analyses are graphically presented with forest plots (Figs.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e, \u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e, \u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003e, \u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e9\u003c/span\u003e, \u003cspan refid=\"Fig11\" class=\"InternalRef\"\u003e11\u003c/span\u003e). For funnel plot generation, two variables are needed: the standard error and the effect size. The standard error was calculated in SPSS using the available sample sizes of the different studies and the effect sizes derived from the forest plot data constructed in JBI SUMARI [\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e]. A funnel plot assessing publication bias was generated in SPSS. Statistical analysis using Egger\u0026rsquo;s test was also performed [\u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e40\u003c/span\u003e]. When a meta-analysis of the data was not possible, the SWiM (synthesis without meta-analysis) approach was used for the synthesis of pooled modifiable musculoskeletal factors [\u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e41\u003c/span\u003e].\u003c/p\u003e"},{"header":"5 Study characteristics","content":"\u003cp\u003eA total of 7628 studies were identified through searching 12 databases (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). An additional eight records were identified through alternative sources (gray literature, thesis and reference lists of articles sourced) and added to the potentially applicable studies. Of these, 3524 duplicates were removed, while another 1253 records were removed for not fulfilling the inclusion criteria. The remainder of the 2870 records were screened by the primary reviewer. A total of 2070 records were excluded because they were not deemed applicable to the review question.\u003c/p\u003e \u003cp\u003eTwo hundred and fifty-one studies were identified and found to be suitable for meeting the inclusion criteria, and the detailed results were imported into the JBI SUMARI [\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e]. The updated search, conducted from the 1st of September 2022 through the 6th of March 2024, yielded one suitable article that met the inclusion criteria of the present systematic review and was incorporated into the present study. The studies were critically screened in a two-step process within the JBI SUMARI [\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e]. First, two independent reviewers (SB and FM-O) screened all the studies at the abstract and title levels, and if deemed appropriate for the review question, the full texts were critically screened.\u003c/p\u003e \u003cp\u003e\u003cdiv id=\"Sec14\" class=\"Section2\"\u003e \u003cp\u003eSixty studies were excluded when scrutinized during the abstract and title screening because they were deemed not applicable to the inclusion criteria for the current systematic review (Figure I). The reasons for the exclusion of both title and abstract and for full-text studies that did not meet the inclusion criteria were recorded and are reported in a table of excluded studies (\u003cspan refid=\"Sec40\" class=\"InternalRef\"\u003eAppendix 2\u003c/span\u003e). No disagreements arose between the reviewers at any stage of the study selection process, and there was no need for intervention by the third reviewer. The results yielded 91 studies that were included in the systematic review. The characteristics of the included studies are described in the Table of Characteristics (Online Resource 2).\u003c/p\u003e \u003cp\u003eThe study designs included were as follows: quasi-experimental\u0026thinsp;=\u0026thinsp;2; case control\u0026thinsp;=\u0026thinsp;2; diagnostic test accuracy\u0026thinsp;=\u0026thinsp;3; cohort\u0026thinsp;=\u0026thinsp;14; case series\u0026thinsp;=\u0026thinsp;2; case report\u0026thinsp;=\u0026thinsp;1; prevalence\u0026thinsp;=\u0026thinsp;1; text and opinion\u0026thinsp;=\u0026thinsp;5; and analytical cross-sectional\u0026thinsp;=\u0026thinsp;46. Sixteen studies provided sufficient data to be pooled into meta-analyses. Age ranged from eighteen years to seventy-five years. A visual depiction of the countries where the studies were conducted can be found in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e.\u003c/p\u003e\u003c/div\u003e"},{"header":"6 Assessing confidence in the findings:","content":"\u003cp\u003eTo assess the association between shoulder dysfunction and the presence of modifiable musculoskeletal factors, the following studies were included in the current systematic review [\u003cspan additionalcitationids=\"CR43 CR44 CR45 CR46 CR47 CR48 CR49 CR50 CR51 CR52 CR53 CR54 CR55 CR56 CR57 CR58 CR59 CR60\" citationid=\"CR42\" class=\"CitationRef\"\u003e42\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR61\" class=\"CitationRef\"\u003e61\u003c/span\u003e, \u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e37\u003c/span\u003e]. Several screening instruments, such as the visual analog scale (VAS) [\u003cspan citationid=\"CR58\" class=\"CitationRef\"\u003e58\u003c/span\u003e, \u003cspan citationid=\"CR62\" class=\"CitationRef\"\u003e62\u003c/span\u003e], overuse injury questionnaire [\u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e], Nordic [\u003cspan citationid=\"CR63\" class=\"CitationRef\"\u003e63\u003c/span\u003e] and Penn Shoulder score [\u003cspan citationid=\"CR64\" class=\"CitationRef\"\u003e64\u003c/span\u003e], were used for reporting the incidence of shoulder pain in the identified primary studies. Due to the heterogeneity of the different pain and dysfunction scales used for reporting pain, the data could not be pooled into a meta-analysis. The incidence of shoulder pain ranged from 27.2% [\u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e] to 55% [\u003cspan citationid=\"CR63\" class=\"CitationRef\"\u003e63\u003c/span\u003e] in the presence of identified modifiable musculoskeletal factors.\u003c/p\u003e \u003cp\u003eThe clinical symptoms and discipline (sport, e.g., tennis; sedentary, e.g., no sport) studied and identified are summarized in the Table of Characteristics (Online Resources 2) and in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e. The etiology of the modifiable musculoskeletal factors causative of shoulder dysfunction was explored with SMD. The Grading of Recommendations, Assessment, Development, and Evaluation (GRADE) [\u003cspan citationid=\"CR65\" class=\"CitationRef\"\u003e65\u003c/span\u003e] approach for assessing confidence in the quality of evidence was used, and a summary of findings (SoF) (Online Resource I) was created. The outcomes reported were SMD (95% CI) and the level of evidence (LOE) determined by the Oxford grading system.\u003c/p\u003e \u003cp\u003eStudies were identified across different subpopulations, ranging from overhead sporting activities to activities of daily living (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e). Data from the primary studies were collected across various sporting fraternities, such as tennis [\u003cspan citationid=\"CR53\" class=\"CitationRef\"\u003e53\u003c/span\u003e], baseball [\u003cspan citationid=\"CR66\" class=\"CitationRef\"\u003e66\u003c/span\u003e], volleyball [\u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e], handball [\u003cspan citationid=\"CR60\" class=\"CitationRef\"\u003e60\u003c/span\u003e], gymnastics (54], weight training [\u003cspan citationid=\"CR55\" class=\"CitationRef\"\u003e55\u003c/span\u003e], rugby [\u003cspan citationid=\"CR58\" class=\"CitationRef\"\u003e58\u003c/span\u003e], wheelchair users [\u003cspan citationid=\"CR67\" class=\"CitationRef\"\u003e67\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR68\" class=\"CitationRef\"\u003e68\u003c/span\u003e] and a sample of members of the public [\u003cspan citationid=\"CR48\" class=\"CitationRef\"\u003e48\u003c/span\u003e] (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eParticipants who were tested via physical testing (n\u0026thinsp;=\u0026thinsp;5558), both female and male participants (F\u0026thinsp;=\u0026thinsp;2441) and (M\u0026thinsp;=\u0026thinsp;3117) were included [\u003cspan additionalcitationids=\"CR43 CR44 CR45 CR46 CR47 CR48 CR49 CR50 CR51 CR52 CR53 CR54 CR55 CR56 CR57 CR58 CR59 CR60\" citationid=\"CR42\" class=\"CitationRef\"\u003e42\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR61\" class=\"CitationRef\"\u003e61\u003c/span\u003e, \u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e37\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eOne study consisted of only a questionnaire (n\u0026thinsp;=\u0026thinsp;5250) completed by both female and male participants [\u003cspan citationid=\"CR63\" class=\"CitationRef\"\u003e63\u003c/span\u003e].\u003c/p\u003e"},{"header":"7 Results","content":"\u003cp\u003eThe Summary of Findings (SoF) Table I and (SoF) (Online Resource I) reflect the results of the included primary studies for the meta-analyses performed. The outcome variables, namely, shoulder dysfunction, where causation was determined, were labeled case (dysfunctional shoulders) and control (non-dysfunctional shoulders).\u003c/p\u003e \u003cp\u003eTo determine the associations between the exposure variables, namely, the modifiable musculoskeletal risk factors ROM, ER and IR and muscle strength (ER and IR), and the outcome variable (shoulder dysfunction), the risk ratio (RR) and odds ratio (OR) were used.\u003c/p\u003e \u003cdiv id=\"Sec17\" class=\"Section2\"\u003e \u003ch2\u003e7.1 Shoulder dysfunction\u003c/h2\u003e \u003c/div\u003e \u003cdiv id=\"Sec18\" class=\"Section2\"\u003e \u003ch2\u003e7.2 Risk analysis\u003c/h2\u003e \u003cp\u003eThe strength of the association between the development of shoulder dysfunction and the presence of modifiable musculoskeletal factors was explored using the RR and OR (Table I and Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e). The extracted results provided by four studies [\u003cspan citationid=\"CR70\" class=\"CitationRef\"\u003e70\u003c/span\u003e, \u003cspan citationid=\"CR58\" class=\"CitationRef\"\u003e58\u003c/span\u003e, \u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e, \u003cspan citationid=\"CR56\" class=\"CitationRef\"\u003e56\u003c/span\u003e] revealed an association between the development of shoulder dysfunction and the incidence of modifiable musculoskeletal factors (Table I).\u003c/p\u003e \u003cp\u003eThe results are expressed from the primary studies pooled into the RR meta-analysis (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e). concluded that participants were at a 1.21-fold increased risk of developing shoulder pain in the presence of decreased IR [\u003cspan citationid=\"CR70\" class=\"CitationRef\"\u003e70\u003c/span\u003e, \u003cspan citationid=\"CR58\" class=\"CitationRef\"\u003e58\u003c/span\u003e, \u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e] and that participants were at a 1.08-fold increased risk of developing shoulder pain in the presence of increased ER (Table I).\u003c/p\u003e \u003cp\u003eDetermining the association between strength and shoulder dysfunction, the OR calculation revealed an increased incidence of 1.29-fold increased risk for patients to present with a supraspinatus tear in the presence of decreased ER strength (Table I) and a 1.18-fold increased risk for presenting with a supraspinatus tear in the presence of decreased abduction strength (Table I). The risk of developing shoulder dysfunction was 1.026 times greater in participants presenting with GIRD [\u003cspan citationid=\"CR71\" class=\"CitationRef\"\u003e71\u003c/span\u003e] (Table I).\u003c/p\u003e \u003cp\u003eA positive association was detected between IR ROM differences [\u003cspan citationid=\"CR70\" class=\"CitationRef\"\u003e70\u003c/span\u003e, \u003cspan citationid=\"CR58\" class=\"CitationRef\"\u003e58\u003c/span\u003e] and an increased incidence of pain in the shoulders of participants, according to the risk ratio calculated in meta-analysis (1) (Table I). A positive association was determined between decreased ER and abduction strength and a supraspinatus tear [\u003cspan citationid=\"CR56\" class=\"CitationRef\"\u003e56\u003c/span\u003e] (Table I). A positive correlation was determined between the development of shoulder dysfunction and GIRD [\u003cspan citationid=\"CR71\" class=\"CitationRef\"\u003e71\u003c/span\u003e] (Table I). Only the ROM primary risk association studies could be pooled into a meta-analysis.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003e(SoF) Risk analysis (RR) and (OR) reported for risk variables of the included primary longitudinal studies.\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"3\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAuthor\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eAssociation measurements (RR/OR) 95% CI\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eRisk factors and incidence of shoulder dysfunction\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eOlivier et al., 2020\u003c/p\u003e \u003cp\u003eLongitudinal cohort\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eRR 1.99 (1.40. 2.59)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eDecreased ROM (IR).\u003c/p\u003e \u003cp\u003eShoulder dysfunction\u0026thinsp;=\u0026thinsp;28%\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMcDonough et al., 2014\u003c/p\u003e \u003cp\u003eLongitudinal\u003c/p\u003e \u003cp\u003ecohort\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eRR 0.42 (-0.21. 1.04)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eDecreased ROM (IR).\u003c/p\u003e \u003cp\u003eShoulder dysfunction\u0026thinsp;=\u0026thinsp;36%\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSkazalski et al., 2020\u003c/p\u003e \u003cp\u003eLongitudinal\u003c/p\u003e \u003cp\u003ecohort\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eOR 1.08 (0.99. 1.17)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eIncreased ROM (ER).\u003c/p\u003e \u003cp\u003eShoulder dysfunction\u0026thinsp;=\u0026thinsp;27.1%\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMiller et al., 2016\u003c/p\u003e \u003cp\u003eLongitudinal\u003c/p\u003e \u003cp\u003ecohort\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eOR 1.18 (1.06. 1.32)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eDecreased ABD strength and supraspinatus tear.\u003c/p\u003e \u003cp\u003eShoulder dysfunction\u0026thinsp;=\u0026thinsp;39%\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMiller et al., 2016\u003c/p\u003e \u003cp\u003eLongitudinal\u003c/p\u003e \u003cp\u003ecohort\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eOR 1.29 (1.14. 1.48)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eDecreased ER strength and supraspinatus tear.\u003c/p\u003e \u003cp\u003eShoulder dysfunction\u0026thinsp;=\u0026thinsp;39%\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eOlivier et al., 2018\u003c/p\u003e \u003cp\u003eLongitudinal\u003c/p\u003e \u003cp\u003ecohort\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eOR 1.001 (1.026. 1.052)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eGIRD and shoulder pain.\u003c/p\u003e \u003cp\u003eShoulder dysfunction\u0026thinsp;=\u0026thinsp;39.2%\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003e \u003csub\u003eRR= risk ratio; OR= odds ratio; ROM=range of motion; IR= internal rotation; ER= external rotation; ABD= abduction; GIRD= glenohumeral internal rotation deficit\u003c/sub\u003e.\u003c/p\u003e \u003cp\u003eAn increase in the risk of developing shoulder dysfunction of 1.26 times was observed in the presence of decreased IR, as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec19\" class=\"Section2\"\u003e \u003ch2\u003e7.3 Etiological analysis\u003c/h2\u003e \u003cp\u003e \u003cem\u003eThe\u003c/em\u003e SMD was used for the reported effect size of the identified modifiable musculoskeletal factors between the cases and the controls (SoF) (Online Resource I). For data collection from the primary studies used for the SMD calculations, measurements were extracted and documented in the following way: strength testing was conducted with either isometric dynamometry or using handheld dynamometers and reported in kilograms (kg) or Newtons (N) (SoF) (Online Resource 1). The results of the tests conducted with an isokinetic dynamometer (Cybex) were reported in Newtons/Kilograms (Nm/kg), and with manual muscle testing techniques, the Oxford grading scale was used.\u003c/p\u003e \u003cp\u003eThe ROM was measured using either a digital or plastic handheld or bubble inclinometer and was documented in degrees. In one study, digital photography was used for measurements of degrees. Kinematic analysis was performed, and the results were documented using inertia motion sensors. For muscle length measurements, calipers, a rigid plastic square, a carpenter square, or a flexible tape measure were used, and the results are reported in centimeters (cm).\u003c/p\u003e \u003cp\u003eThe etiology of the development of shoulder dysfunction was based on the following modifiable musculoskeletal factors: the rotator cuff musculature, the strength ratio of the inferior cuff (external versus internal strength), the supraspinatus muscle, differences in the length of the pectoralis minor muscle, the latissimus dorsi muscle length and posterior capsule flexibility. Specifically, the ROM, IR, GIRD, posterior capsule tightness (PCT), horizontal adduction (Hadd), total range of motion (TROM), external rotation gain (ERG), external rotation deficit (ERD) of the glenohumeral joint, pectoralis minor muscle changes and scapular dyskinesis were reported. The previously mentioned exposure variables have been highlighted in this review in the findings and \u003cspan refid=\"Sec28\" class=\"InternalRef\"\u003ediscussion\u003c/span\u003e sections (Online Resource I) [\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e, \u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e, \u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e37\u003c/span\u003e, \u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e42\u003c/span\u003e, \u003cspan additionalcitationids=\"CR45 CR46 CR47 CR48 CR49 CR50 CR51 CR52 CR53\" citationid=\"CR44\" class=\"CitationRef\"\u003e44\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR54\" class=\"CitationRef\"\u003e54\u003c/span\u003e, \u003cspan additionalcitationids=\"CR57 CR58 CR59 CR60 CR61\" citationid=\"CR56\" class=\"CitationRef\"\u003e56\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR62\" class=\"CitationRef\"\u003e62\u003c/span\u003e, \u003cspan citationid=\"CR64\" class=\"CitationRef\"\u003e64\u003c/span\u003e, \u003cspan citationid=\"CR66\" class=\"CitationRef\"\u003e66\u003c/span\u003e, \u003cspan citationid=\"CR68\" class=\"CitationRef\"\u003e68\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR69\" class=\"CitationRef\"\u003e69\u003c/span\u003e, \u003cspan additionalcitationids=\"CR71 CR72 CR73 CR74 CR75 CR76 CR77 CR78 CR79 CR80 CR81\" citationid=\"CR70\" class=\"CitationRef\"\u003e70\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR82\" class=\"CitationRef\"\u003e82\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eThe modifiable musculoskeletal factor variables were compared between the cases and controls among both females and males in the included primary studies.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec20\" class=\"Section2\"\u003e \u003ch2\u003e7.4 Muscle Strength\u003c/h2\u003e \u003c/div\u003e \u003cdiv id=\"Sec21\" class=\"Section2\"\u003e \u003ch2\u003e7.5 External rotation strength\u003c/h2\u003e \u003cp\u003eThe second meta-analysis (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e) reported the ER strength of the cases and the controls, and enough homogeneity was present between the studies, using the means and standard deviation (SD) to be pooled into meta-analyses. The participants were measured with isokinetic and isometric dynamometers. The SMD was calculated using the random-effects model for ER strength.\u003c/p\u003e \u003cp\u003eIn meta-analysis (2), a high heterogeneity of I\u003csup\u003e2\u003c/sup\u003e\u0026thinsp;=\u0026thinsp;74 and a moderate effect size of 0.54 (95% CI, 0.22\u0026ndash;0.85) with a significance of P\u0026thinsp;=\u0026thinsp;0.001 were present, with the results favoring increased ER strength in the controls (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e). Potential sources of heterogeneity could be attributed to age differences between the participants, sex differences and the different testing methods employed. After sensitivity analysis was conducted, the heterogeneity decreased (I\u003csup\u003e2\u003c/sup\u003e\u0026thinsp;=\u0026thinsp;0), and a small negative effect size of -0.29 (95% CI, -0.80-0.40) and a nonsignificant difference (p\u0026thinsp;=\u0026thinsp;0.85) were detected (Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e). The results still favored stronger ER strength values in favor of the controls.\u003c/p\u003e \u003cp\u003ePublication bias was assessed using a funnel plot (Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003e), and no publication bias was detected.\u003c/p\u003e \u003cp\u003eIn an effort to reduce heterogeneity, a study testing isokinetic external rotator cuff strength [\u003cspan citationid=\"CR60\" class=\"CitationRef\"\u003e60\u003c/span\u003e] (SoF) (Online Resource I) was removed from the meta-analysis. To further reduce heterogeneity, a sub analysis of studies with similar sample sizes was performed [\u003cspan citationid=\"CR53\" class=\"CitationRef\"\u003e53\u003c/span\u003e, \u003cspan citationid=\"CR78\" class=\"CitationRef\"\u003e78\u003c/span\u003e, \u003cspan citationid=\"CR48\" class=\"CitationRef\"\u003e48\u003c/span\u003e]. (SoF) (Online Resource I) were constructed. The heterogeneity decreased to I\u003csup\u003e2\u003c/sup\u003e\u0026thinsp;=\u0026thinsp;0%. The overall results still supported the use of stronger external rotators for the controls, with a large positive effect size of 0.59.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec22\" class=\"Section2\"\u003e \u003ch2\u003e7.6 External (ER): Internal (IR) strength ratio\u003c/h2\u003e \u003cp\u003eThe following meta-analysis (3) in Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003e presents the ER:IR strength ratio between the cases and the controls of the included pooled studies. Pooling of studies investigating ER:IR strength ratios between the cases and the controls made it possible to employ the means and SDs to estimate the SMD with a random-effects model in a meta-analysis.\u003c/p\u003e \u003cp\u003eWith a statistically significant presence (p\u0026thinsp;=\u0026thinsp;0.002), medium heterogeneity (I\u003csup\u003e2\u003c/sup\u003e\u0026thinsp;=\u0026thinsp;46) and a large negative effect size of -0.69, as depicted in Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003e, overall lower ER:IR strength ratios are shown to favor these patients.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec23\" class=\"Section2\"\u003e \u003ch2\u003e7.7 Internal Rotation ROM\u003c/h2\u003e \u003cp\u003eMeta-analysis (4) revealed the difference in the IR ROM between the cases and the controls (Fig.\u0026nbsp;\u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e9\u003c/span\u003e). Pooling of studies investigating internal rotation between the cases and the controls was possible by employing the means and SDs to estimate the SMD with a random-effects model in a meta-analysis (Fig.\u0026nbsp;\u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e9\u003c/span\u003e). Even though a high level of heterogeneity was present (I\u003csup\u003e2\u003c/sup\u003e\u0026thinsp;=\u0026thinsp;77), a large negative effect size of -0.62 (95% CI, -0.95:0.28) was determined, favoring the cases.\u003c/p\u003e\u003cp\u003eAccording to the sensitivity analysis (Fig.\u0026nbsp;\u003cspan refid=\"Fig10\" class=\"InternalRef\"\u003e10\u003c/span\u003e), after removing participants from larger sample sizes and grouping similar subgroups, such as tennis players together, less heterogeneity was demonstrated (I\u003csup\u003e2\u003c/sup\u003e\u0026thinsp;=\u0026thinsp;0), with a large negative effect size of -1.00 (95% CI, -1.30: -0.70). The results still favored the cases [\u003cspan citationid=\"CR53\" class=\"CitationRef\"\u003e53\u003c/span\u003e, \u003cspan citationid=\"CR72\" class=\"CitationRef\"\u003e72\u003c/span\u003e, \u003cspan citationid=\"CR78\" class=\"CitationRef\"\u003e78\u003c/span\u003e].\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec24\" class=\"Section2\"\u003e \u003ch2\u003e7.8 GIRD\u003c/h2\u003e \u003cp\u003eMeta-analysis (5) explored the GIRD of the cases (Fig.\u0026nbsp;\u003cspan refid=\"Fig11\" class=\"InternalRef\"\u003e11\u003c/span\u003e). When the means and SDs were pooled with the random effects model to determine the SMD, heterogeneity was not detected (I\u003csup\u003e2\u003c/sup\u003e\u0026thinsp;=\u0026thinsp;0), with a small negative effect size of -0.10 (95% CI, -0.36:0.16) favoring the cases.\u003c/p\u003e\u003c/div\u003e \u003cdiv id=\"Sec25\" class=\"Section2\"\u003e \u003ch2\u003e7.9 Muscle flexibility of the cases and the controls\u003c/h2\u003e \u003c/div\u003e \u003cdiv id=\"Sec26\" class=\"Section2\"\u003e \u003ch2\u003e7.10 Pectoralis minor\u003c/h2\u003e \u003cp\u003eThe muscle length of the pectoralis minor muscle (PMm) was investigated in terms of the muscle indices; muscle shortening; muscle lengthening; muscle activity; muscle rest; and muscle length in different testing positions [\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e, \u003cspan citationid=\"CR57\" class=\"CitationRef\"\u003e57\u003c/span\u003e, \u003cspan citationid=\"CR64\" class=\"CitationRef\"\u003e64\u003c/span\u003e, \u003cspan citationid=\"CR67\" class=\"CitationRef\"\u003e67\u003c/span\u003e, \u003cspan citationid=\"CR70\" class=\"CitationRef\"\u003e70\u003c/span\u003e, \u003cspan citationid=\"CR72\" class=\"CitationRef\"\u003e72\u003c/span\u003e, \u003cspan citationid=\"CR75\" class=\"CitationRef\"\u003e75\u003c/span\u003e, \u003cspan additionalcitationids=\"CR83 CR84 CR85 CR86 CR87 CR88 CR89 CR90 CR91\" citationid=\"CR82\" class=\"CitationRef\"\u003e82\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR92\" class=\"CitationRef\"\u003e92\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eTwo main physical examination-based measurements for the pectoralis minor muscle were identified and used by various authors in the study of both cases and controls: the pectoralis minor index (PMI) test described by Borstad [\u003cspan citationid=\"CR93\" class=\"CitationRef\"\u003e93\u003c/span\u003e] and the pectoralis minor length test (PMLT) described by Kendall [\u003cspan citationid=\"CR94\" class=\"CitationRef\"\u003e94\u003c/span\u003e]. Full details are available in (SoF) (Online Resource I) and (Table of Characteristics) (Online Resource 2).\u003c/p\u003e \u003cp\u003eThe results of the studies that investigated PMm flexibility could not be pooled into a meta-analysis due to heterogeneity in the measurement methods used. The characteristics of pectoralis minor were pooled together, and the results are summarized in tabular formats (Table of Characteristics) (Online Resource 2) and in (SoF) (Online Resource I.). A positive trend between changes in PMm flexibility and the cases has been established with the current systematic review. The derivation results are fully discussed in the \u003cspan refid=\"Sec28\" class=\"InternalRef\"\u003ediscussion\u003c/span\u003e section.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec27\" class=\"Section2\"\u003e \u003ch2\u003e7.11 Scapular kinematics\u003c/h2\u003e \u003cp\u003eScapular kinematics, dyskinesis and EMG studies of the scapular stabilizers were performed by the following authors: [\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e, \u003cspan citationid=\"CR48\" class=\"CitationRef\"\u003e48\u003c/span\u003e, \u003cspan citationid=\"CR61\" class=\"CitationRef\"\u003e61\u003c/span\u003e, \u003cspan citationid=\"CR76\" class=\"CitationRef\"\u003e76\u003c/span\u003e, \u003cspan citationid=\"CR84\" class=\"CitationRef\"\u003e84\u003c/span\u003e, \u003cspan citationid=\"CR86\" class=\"CitationRef\"\u003e86\u003c/span\u003e, \u003cspan citationid=\"CR88\" class=\"CitationRef\"\u003e88\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR89\" class=\"CitationRef\"\u003e89\u003c/span\u003e, \u003cspan additionalcitationids=\"CR96\" citationid=\"CR95\" class=\"CitationRef\"\u003e95\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR97\" class=\"CitationRef\"\u003e97\u003c/span\u003e]. The results are highlighted, discussed and tabularized in the \u0026ldquo;SoF\u0026rdquo; section (Online Resource I) and in the \u0026ldquo;Table of Characteristics\u0026rdquo; section (Online Resource 2).\u003c/p\u003e \u003c/div\u003e"},{"header":"8 Discussion","content":"\u003cdiv id=\"Sec29\" class=\"Section2\"\u003e \u003ch2\u003e8.1 Association between modifiable musculoskeletal risk factors and the development of shoulder dysfunction\u003c/h2\u003e \u003cp\u003eThis was the first systematic review, to the authors\u0026rsquo; knowledge, to investigate multiple known modifiable musculoskeletal factors and their association with the development of shoulder dysfunction at one point in time. All currently available evidence was summarized, analyzed and methodologically appraised (Online Resources I, 2). The current systematic review included cross-sectional and longitudinal studies investigating numerous sporting populations (swimming, rugby, weightlifting, wheelchair sports, volleyball and baseball (1003 participants)) and members of the general population (4651). The studies included both females (2441) and males (3117).\u003c/p\u003e \u003cp\u003eAn increased risk of developing shoulder dysfunction in the presence of modifiable musculoskeletal factors was determined with the RR and OR analysis of the present systematic review (Table I). Risk analysis revealed that the incidence of both ROM and strength changes in the presence of modifiable musculoskeletal factors in dysfunctional shoulders [\u003cspan citationid=\"CR70\" class=\"CitationRef\"\u003e70\u003c/span\u003e, \u003cspan citationid=\"CR58\" class=\"CitationRef\"\u003e58\u003c/span\u003e]. The strength of the association between exposure and outcome was tested by pooling studies into several meta-analyses (Figs.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e, \u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e, \u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003e, \u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e9\u003c/span\u003e, \u003cspan refid=\"Fig11\" class=\"InternalRef\"\u003e11\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eVery little bony support is provided to the glenohumeral and scapulothoracic joints, which are mainly controlled by contractile and noncontractile muscular forces [\u003cspan citationid=\"CR98\" class=\"CitationRef\"\u003e98\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR99\" class=\"CitationRef\"\u003e99\u003c/span\u003e]. Participants studied with EMG analysis and presented with subacromial impingement demonstrated decreased activation of the subscapularis-infraspinatus and supraspinatus-infraspinatus force couples and increased middle deltoid activation at the start of elevation (0\u0026deg;\u0026ndash;30\u0026deg;) [\u003cspan citationid=\"CR100\" class=\"CitationRef\"\u003e100\u003c/span\u003e]. Recent research by Millet [\u003cspan citationid=\"CR101\" class=\"CitationRef\"\u003e101\u003c/span\u003e] proposed that in subacromial impingement syndrome, the force vector of the supraspinatus that counterbalances the upward directed force of the deltoid might be disrupted. Weakness and thus decreased proprioception of the infraspinatus disrupt the force couple of the rotator cuff and destabilize the glenohumeral joint on the glenoid [\u003cspan citationid=\"CR102\" class=\"CitationRef\"\u003e102\u003c/span\u003e]. These historical results will be discussed next considering the conclusions drawn from the current systematic review.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec30\" class=\"Section2\"\u003e \u003ch2\u003e8.2 Strength\u003c/h2\u003e \u003cp\u003eNumerous authors [\u003cspan citationid=\"CR54\" class=\"CitationRef\"\u003e54\u003c/span\u003e, \u003cspan citationid=\"CR58\" class=\"CitationRef\"\u003e58\u003c/span\u003e, \u003cspan citationid=\"CR60\" class=\"CitationRef\"\u003e60\u003c/span\u003e, \u003cspan citationid=\"CR66\" class=\"CitationRef\"\u003e66\u003c/span\u003e] of the included primary studies used for the generation of strength meta-analyses agree that stronger external rotators contribute to shoulder stability and, in their opinion, lessen the chances of developing shoulder dysfunction. In primary studies conducted on the strength differences of nondysfunctional shoulders of overhead athletes and in a convenience sample of members of the general population, no difference in side-to-side strength was found [\u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e37\u003c/span\u003e, \u003cspan additionalcitationids=\"CR50\" citationid=\"CR49\" class=\"CitationRef\"\u003e49\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR51\" class=\"CitationRef\"\u003e51\u003c/span\u003e, \u003cspan citationid=\"CR60\" class=\"CitationRef\"\u003e60\u003c/span\u003e, \u003cspan citationid=\"CR103\" class=\"CitationRef\"\u003e103\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eNot all published data from identified studies reporting strength measurements could be used for pooling results due to methodological differences. A study by Wong [\u003cspan citationid=\"CR47\" class=\"CitationRef\"\u003e47\u003c/span\u003e] reported the normalized fatigue ratios and the peak ratios of cases and control participants, but due to the difference in measurement properties, the data could not be incorporated into strength meta-analyses. Their main conclusions reflected an expressed lower peak torque reached in concentric ER in the cases in comparison to the controls.\u003c/p\u003e \u003cp\u003eThe decreased strength of the external rotator as well as of the supraspinatus may be linked to pain inhibition as the causative factor. However, Lajtai [\u003cspan citationid=\"CR104\" class=\"CitationRef\"\u003e104\u003c/span\u003e] determined that atrophy of the infraspinatus was present in the painful shoulders of beachball volleyball payers. The difference in strength was a mean of 2.3 kg between the painful and nonpainful sides. A decrease in the cross-sectional area of the supraspinatus in the presence of painful shoulders was observed by Benitez-Martinez [\u003cspan citationid=\"CR105\" class=\"CitationRef\"\u003e105\u003c/span\u003e]. Therefore, the authors believe that the decreased muscle strength observed in the affected tissues (infraspinatus and supraspinatus) may be responsible for the decrease in strength observed in the ER, and the observed differences in strength may not be solely due to pain inhibition.\u003c/p\u003e \u003cp\u003eConsidering the overall conclusions reached from the strength meta-analyses (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e, \u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003e), strengthening the ER, especially through eccentric control of the ER in overhead athletes, might be advisable to offset strong IR. This prevents the development of ER fatigue with repetitive overhead throwing motions, predisposing an athlete to injury. Hence, it could be hypothesized that a stronger ER may be beneficial for shoulder stability in all healthy shoulders regardless of the activity performed.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec31\" class=\"Section2\"\u003e \u003ch2\u003e8.3 Ratio of the ER:IR strength\u003c/h2\u003e \u003cp\u003eIn the present systematic review, strength ratios were explored in most populations, including members of the general population. The results of the primary studies [\u003cspan citationid=\"CR53\" class=\"CitationRef\"\u003e53\u003c/span\u003e, \u003cspan citationid=\"CR58\" class=\"CitationRef\"\u003e58\u003c/span\u003e, \u003cspan citationid=\"CR106\" class=\"CitationRef\"\u003e106\u003c/span\u003e] reflected higher strength ratios to favor the controls in both overhead, underhand and members of the general population (Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003e). Even though some caution should be given to the conclusions, given the presence of a statistically significant (p\u0026thinsp;=\u0026thinsp;0.002) medium effect size, a higher ER:IR ratio was found in favor of the controls. Although not pooled into a meta-analysis, the results obtained in another systematic review [\u003cspan citationid=\"CR108\" class=\"CitationRef\"\u003e108\u003c/span\u003e], which was not pooled into a meta-analysis and was conducted on an overhead athletic population, concurred with the results of the current SR, which showed that a low strength ratio (ER:IR) is predictive of the development of shoulder dysfunction. These findings were reiterated in previous studies of overhead athletes by Saccol [\u003cspan citationid=\"CR108\" class=\"CitationRef\"\u003e108\u003c/span\u003e], who concluded that no significant difference in strength was present in the isometric ER:IR strength ratios in asymptomatic athletes.\u003c/p\u003e \u003cp\u003eA different testing procedure was employed by Peckitt [\u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e37\u003c/span\u003e] in that they tested cricket players preseason and in-season to monitor strength changes present at baseline and those developed during season on both the dominant and nondominant sides. Therefore, the data could not be incorporated into any of the strength meta-analyses because they did not fit any of the case or control categories of the present systematic review. Their main conclusion was that the dominant ER:IR strength ratio was lower, with a mean ER of 0.71 (0.13) versus an IR of 0.93 (0.21) at baseline testing of players predisposed to developing arm trouble in-season. The results can be found in the Table of Characteristics (Online Resource 2) and (Online Resource I). In contrast to previous reports, McDonough [\u003cspan citationid=\"CR58\" class=\"CitationRef\"\u003e58\u003c/span\u003e] investigated the dynamic control ratio (DCR) of the IR:ER in rugby league players. The authors tested the eccentric internal (Ecc/IR) and concentric external (Conn/ER) rotator cuff strengths in the 90-degree abducted position via isotonic testing of the inferior rotator cuff. Their main conclusion was that the (Ecc/IR: Conn/ER) ratio of the injured to the noninjured shoulder was lower (IR:ER) (1.84:1.71) on the left side than on the right side (IR:ER) (1.97:1.69). The authors recommended strengthening the internal rotator cuff to prevent injury.\u003c/p\u003e \u003cp\u003eThe nature of overhead sports requires the player\u0026rsquo;s dominant arm to generate higher strength values of the IR for execution of the sporting motion. Increased IR strength values leading to different ER:IR ratios were determined in handball players [\u003cspan citationid=\"CR51\" class=\"CitationRef\"\u003e51\u003c/span\u003e, \u003cspan citationid=\"CR60\" class=\"CitationRef\"\u003e60\u003c/span\u003e]. Therefore, functional ratios lower than the ER:IR (1.00:1.00) ratio recommended in the literature have been observed [\u003cspan citationid=\"CR51\" class=\"CitationRef\"\u003e51\u003c/span\u003e, \u003cspan citationid=\"CR58\" class=\"CitationRef\"\u003e58\u003c/span\u003e]. It is suggested that eccentric external rotation (eccER) should be stronger than concentric internal rotation (connIR) to compensate for the deceleration and control of the glenohumeral head (GH) in the throwing motion in overhead sports. Numerous authors of the included primary studies agree that a higher ER:IR strength ratio prevents the development of shoulder dysfunction [\u003cspan citationid=\"CR50\" class=\"CitationRef\"\u003e50\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR51\" class=\"CitationRef\"\u003e51\u003c/span\u003e, \u003cspan citationid=\"CR58\" class=\"CitationRef\"\u003e58\u003c/span\u003e, \u003cspan citationid=\"CR60\" class=\"CitationRef\"\u003e60\u003c/span\u003e, \u003cspan citationid=\"CR108\" class=\"CitationRef\"\u003e108\u003c/span\u003e].\u003c/p\u003e \u003cp\u003e.\u003c/p\u003e \u003cp\u003eA decrease in the subacromial space (SAS) was observed in the presence of a stronger IR. A stronger IR resulted in a decreased ER:IR agonistic-antagonistic force couple ratio. A decreased SAS leads to impingement of the rotator cuff (RC) in the abduction motion from 0\u0026deg; to 60\u0026deg; [\u003cspan citationid=\"CR47\" class=\"CitationRef\"\u003e47\u003c/span\u003e]. This decreased ER:IR ratio had a knock-on effect on destabilizing the dynamic control of the humeral head on the glenoid in overhead sports, such as softball, leading to SIS [\u003cspan citationid=\"CR47\" class=\"CitationRef\"\u003e47\u003c/span\u003e].\u003c/p\u003e \u003cp\u003e.\u003c/p\u003e \u003cp\u003eRegardless of the shoulder motion required or strength of evidence provided, strengthening and restoring the ER:IR force couple to a better strength ratio is deemed advisable for improved shoulder stability in both athletes and members of the general population.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec32\" class=\"Section2\"\u003e \u003ch2\u003e8.4 IR ROM\u003c/h2\u003e \u003cp\u003eDecreased internal rotation has been identified as a precursor to developing shoulder dysfunction by various authors of the included primary studies pooled into a meta-analysis (4) (Fig.\u0026nbsp;\u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e9\u003c/span\u003e) [\u003cspan citationid=\"CR53\" class=\"CitationRef\"\u003e53\u003c/span\u003e, \u003cspan citationid=\"CR72\" class=\"CitationRef\"\u003e72\u003c/span\u003e, \u003cspan citationid=\"CR77\" class=\"CitationRef\"\u003e77\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR78\" class=\"CitationRef\"\u003e78\u003c/span\u003e]. Populations included overhead sports such as cricket, handball and tennis, as well as members of the general population [\u003cspan citationid=\"CR48\" class=\"CitationRef\"\u003e48\u003c/span\u003e]. IR must not be measured in isolation; however, ER and TROM should be measured and considered at the same time. In overhead sports, particularly baseball, a symmetrical loss of IR is often offset by a symmetrical gain in ER ROM [\u003cspan citationid=\"CR74\" class=\"CitationRef\"\u003e74\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eIt was noted that the presence of IR ROM was less pronounced, even though still present, in a sample of the general public than in sporting populations, such as in overhead sports, tennis, handball, cricket, swimming, and underhand sports (rugby) [37,48,72,78\u0026thinsp;\u0026minus;\u0026thinsp;77] (Table\u0026nbsp;9). Several studies have shown that players complaining of shoulder pain from posterosuperior internal impingement present with decreased IR and ER and a decreased total arch of movement (TAM) [\u003cspan citationid=\"CR77\" class=\"CitationRef\"\u003e77\u003c/span\u003e, \u003cspan citationid=\"CR72\" class=\"CitationRef\"\u003e72\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eWith an overall side-to-side comparison of the included primary studies of the present SR, a general decrease in TROM was determined, which indicated that both ER and IR decreased. This was also found in populations such as tennis, cricket, handball, swimming and underhand (rugby) [\u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e37\u003c/span\u003e, \u003cspan citationid=\"CR58\" class=\"CitationRef\"\u003e58\u003c/span\u003e, \u003cspan citationid=\"CR72\" class=\"CitationRef\"\u003e72\u003c/span\u003e, \u003cspan citationid=\"CR77\" class=\"CitationRef\"\u003e77\u003c/span\u003e] and in members of the general public [\u003cspan citationid=\"CR48\" class=\"CitationRef\"\u003e48\u003c/span\u003e]. This phenomenon was not observed for baseball players [\u003cspan citationid=\"CR110\" class=\"CitationRef\"\u003e110\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR111\" class=\"CitationRef\"\u003e111\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eIt can therefore be surmised that decreased IR and increased ER might be more common in subdisciplines such as baseball, where extremely high velocities are generated in the overhead throwing motion, potentially leading to compensatory imbalance between the ER and the IR.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec33\" class=\"Section2\"\u003e \u003ch2\u003e8.5 GIRD\u003c/h2\u003e \u003cp\u003eGIRD has been linked to an increased risk of developing shoulder dysfunction by several of the authors of the included primary studies of the present systematic review in overhead sports such as tennis and handball at a professional level [72,78\u0026thinsp;\u0026minus;\u0026thinsp;77]. The pooled results are summarized in the meta-analysis (5) (Fig.\u0026nbsp;\u003cspan refid=\"Fig11\" class=\"InternalRef\"\u003e11\u003c/span\u003e). Even though not covered in the present systematic review, when considering limited IR, osseous adaptation should also be considered a contributing factor to the limitation of IR. This approach is especially applicable in overhead sports, such as baseball [\u003cspan citationid=\"CR74\" class=\"CitationRef\"\u003e74\u003c/span\u003e]. Reuther [\u003cspan citationid=\"CR74\" class=\"CitationRef\"\u003e74\u003c/span\u003e] observed that if humeral retroversion is corrected in the presence of the measured GIRD, the GIRD disappears; thus, soft tissue changes are not solely responsible for the GIRD.\u003c/p\u003e \u003cp\u003eLubiatowski [\u003cspan citationid=\"CR77\" class=\"CitationRef\"\u003e77\u003c/span\u003e] reported that a greater incidence of shoulder pain was present in patients with internal deficits of more than 20 degrees. A GIRD of up to 41 degrees has been determined in the symptomatic shoulders of individuals in a general population group [\u003cspan citationid=\"CR112\" class=\"CitationRef\"\u003e112\u003c/span\u003e]. A greater incidence of internal impingement was present when both internal deficits of more than 25 degrees and a total arch of motion of more than 20 degrees coexisted [\u003cspan citationid=\"CR77\" class=\"CitationRef\"\u003e77\u003c/span\u003e]. Total arch of motion deficits (TAMDs) of between 6 degrees to 16.7 have been found in pathological shoulders [\u003cspan citationid=\"CR77\" class=\"CitationRef\"\u003e77\u003c/span\u003e, \u003cspan citationid=\"CR78\" class=\"CitationRef\"\u003e78\u003c/span\u003e] (Online Resource 1). This is more than the 5-degree results obtained in the original study proposed by Wilk [\u003cspan citationid=\"CR111\" class=\"CitationRef\"\u003e111\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eThe overall conclusions reached in the study of skilled amateur tennis players were that GIRD, posterior capsule tightness, external rotation strength deficits and ERG were present in combination in the clinical presence of internal impingement and the superior labral anterior posterior region.\u003c/p\u003e \u003cp\u003eCompared with those in the controls, (SLAP) lesions existed in the symptomatic dominant arm of the players [\u003cspan citationid=\"CR53\" class=\"CitationRef\"\u003e53\u003c/span\u003e]. Posterosuperior internal impingement was associated with decreased IR, ER and TAM, as well as greater TAMD and GIRD, in tennis players with pain than in tennis players without pain in their primary study [\u003cspan citationid=\"CR53\" class=\"CitationRef\"\u003e53\u003c/span\u003e]. Additionally, GIRD has been associated with posterior capsule thickening and stiffness as well as internal impingement.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec34\" class=\"Section2\"\u003e \u003ch2\u003e8.6 Posterior capsule\u003c/h2\u003e \u003cp\u003eStructures that can cause a decrease in IR are the posterior inferior cuff (infraspinatus and teres minor) and the posterior capsule [\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e, \u003cspan citationid=\"CR113\" class=\"CitationRef\"\u003e113\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR114\" class=\"CitationRef\"\u003e114\u003c/span\u003e].\u003c/p\u003e \u003cp\u003ePosteroinferior shortening of the abovementioned structures results in a posterosuperior shift of the humerus, causing internal impingement [\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e, \u003cspan citationid=\"CR115\" class=\"CitationRef\"\u003e115\u003c/span\u003e]. This phenomenon can potentially maximize the peel-back forces of the long head of the biceps and predispose an athlete to developing SLAP lesions [\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e, \u003cspan citationid=\"CR116\" class=\"CitationRef\"\u003e116\u003c/span\u003e]. GIRD not only occurs in baseball players, as originally described by Pappas [\u003cspan citationid=\"CR114\" class=\"CitationRef\"\u003e114\u003c/span\u003e] and Burkhart [\u003cspan citationid=\"CR117\" class=\"CitationRef\"\u003e117\u003c/span\u003e] but also occurs in other overhead disciples, such as skilled amateur tennis players [\u003cspan citationid=\"CR53\" class=\"CitationRef\"\u003e53\u003c/span\u003e, \u003cspan citationid=\"CR113\" class=\"CitationRef\"\u003e113\u003c/span\u003e], handball players [\u003cspan citationid=\"CR77\" class=\"CitationRef\"\u003e77\u003c/span\u003e] and cricket players [\u003cspan citationid=\"CR57\" class=\"CitationRef\"\u003e57\u003c/span\u003e].\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec35\" class=\"Section2\"\u003e \u003ch2\u003e8.7 ER gain\u003c/h2\u003e \u003cp\u003ePartial rotator cuff tears (RCTs) were accompanied by greater ER and total arch of movement gain (TAMG) in a study of professional handball players [\u003cspan citationid=\"CR77\" class=\"CitationRef\"\u003e77\u003c/span\u003e]. The findings are described in detail in the online supplement (Online Resource I).\u003c/p\u003e \u003cp\u003eNo difference was observed in either ROM or strength during the preseason on gymnasts between athletes sustaining an injury and injury-free athletes [\u003cspan citationid=\"CR54\" class=\"CitationRef\"\u003e54\u003c/span\u003e]. The bilateral nature of the sport may provide a link to the lack of observed differences [\u003cspan citationid=\"CR54\" class=\"CitationRef\"\u003e54\u003c/span\u003e].\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec36\" class=\"Section2\"\u003e \u003ch2\u003e8.8 Pectoralis minor\u003c/h2\u003e \u003cp\u003eShortening of the pectoralis minor has been identified as contributing to scapula dyskinesis [\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e, \u003cspan citationid=\"CR96\" class=\"CitationRef\"\u003e96\u003c/span\u003e, \u003cspan citationid=\"CR119\" class=\"CitationRef\"\u003e119\u003c/span\u003e]. The results of the primary studies included in the current systematic review revealed that a shortened PMm can cause anterior tilt, protraction and internal rotation of the scapula [\u003cspan citationid=\"CR99\" class=\"CitationRef\"\u003e99\u003c/span\u003e, \u003cspan citationid=\"CR119\" class=\"CitationRef\"\u003e119\u003c/span\u003e]. This places the scapular stabilizing muscles, particularly the lower fibers of the trapezius and the serratus anterior lower fibers, in a biomechanically altered position with reduced posterior tilt of the scapula [\u003cspan citationid=\"CR99\" class=\"CitationRef\"\u003e99\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eDecreased flexibility of the PMm and ER was noted after a bout of swimming in the painful group of swimmers [\u003cspan citationid=\"CR64\" class=\"CitationRef\"\u003e64\u003c/span\u003e]. Increased PMm activity occurred in a painful group of participants who presented with SIS in a laboratory-controlled group [\u003cspan citationid=\"CR84\" class=\"CitationRef\"\u003e84\u003c/span\u003e]. Decreased IR and ER decreased the flexibility of the PMm and the posterior capsule, as did [\u003cspan citationid=\"CR57\" class=\"CitationRef\"\u003e57\u003c/span\u003e], which determined the weakness of the SA in their study of cricket players. Decreased flexibility of the PMm was observed in wheelchair users [\u003cspan citationid=\"CR67\" class=\"CitationRef\"\u003e67\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eDecreased flexibility of the pectoralis minor and the latissimus dorsi was associated with an increase in pain in competitive swimmers [\u003cspan citationid=\"CR119\" class=\"CitationRef\"\u003e119\u003c/span\u003e]. The presence of scapular dyskinesis has also been observed with alterations in the PMm using different measurement methods [\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e, \u003cspan citationid=\"CR44\" class=\"CitationRef\"\u003e44\u003c/span\u003e, \u003cspan additionalcitationids=\"CR86 CR87 CR88 CR89\" citationid=\"CR85\" class=\"CitationRef\"\u003e85\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR90\" class=\"CitationRef\"\u003e90\u003c/span\u003e, \u003cspan citationid=\"CR120\" class=\"CitationRef\"\u003e120\u003c/span\u003e]. See (SoF) (Online Resource I) and Table of Characteristics (Online Resource 2).\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec37\" class=\"Section2\"\u003e \u003ch2\u003e8.9 Scapular dyskinesis\u003c/h2\u003e \u003cp\u003eNumerous authors have investigated the presence of scapular dyskinesis and its relevance [\u003cspan citationid=\"CR46\" class=\"CitationRef\"\u003e46\u003c/span\u003e, \u003cspan citationid=\"CR61\" class=\"CitationRef\"\u003e61\u003c/span\u003e, \u003cspan citationid=\"CR76\" class=\"CitationRef\"\u003e76\u003c/span\u003e, \u003cspan additionalcitationids=\"CR122\" citationid=\"CR121\" class=\"CitationRef\"\u003e121\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR123\" class=\"CitationRef\"\u003e123\u003c/span\u003e] in both athletic and nonathletic population groups. Heterogeneity within the measurement properties used for scapular kinematics prevented pooling of studies. The SWiM approach was used, and the results of the identified studies are summarized in the Table of Characteristics (Online Resource 2) [\u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e41\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eIn their text and opinion study, Saini [\u003cspan citationid=\"CR122\" class=\"CitationRef\"\u003e122\u003c/span\u003e] highlighted the importance of the early identification and correction of observed scapular dyskinesis in tennis players. The control and position of the scapula are dependent mainly on scapular stabilizers due to an inherent lack of bony stability. Therefore, the abovementioned imbalance in the scapular stabilizers of the included studies may be clinically relevant. Phadke [\u003cspan citationid=\"CR123\" class=\"CitationRef\"\u003e123\u003c/span\u003e] concluded that decreased strength of the lower trapezius leads to less upward rotation of the scapula. Huang [\u003cspan citationid=\"CR76\" class=\"CitationRef\"\u003e76\u003c/span\u003e] observed increased upper trapezius activity in the presence of scapular inferior angle prominence in symptomatic shoulders.\u003c/p\u003e \u003cp\u003eMoreover, Kolber [\u003cspan citationid=\"CR46\" class=\"CitationRef\"\u003e46\u003c/span\u003e] reported the presence of increased strength of the upper trapezius in weightlifters with subacromial impingement (SIS). Borstad and Ludwig [\u003cspan citationid=\"CR121\" class=\"CitationRef\"\u003e121\u003c/span\u003e] investigated scapular kinematics with a motion sensor (Fastrak) and concluded that less upward rotation was present at lower angles and more anterior tipping of the scapula was present at greater angles of elevation in symptomatic shoulders. The positioning of the scapula is mainly controlled by scapular stabilizers and imbalances in muscle strength, and more important force couples in these muscles may lead to abnormal positioning of the scapula, which has a negative impact on the functioning of the glenohumeral joint.\u003c/p\u003e \u003cp\u003eThe previously mentioned imbalances in scapular stabilizers, as highlighted by various researchers, can hence lead to scapular dyskinesis or dyskinesia. However, an interesting observation of decreased muscle strength of the rotator cuff was made by [\u003cspan citationid=\"CR61\" class=\"CitationRef\"\u003e61\u003c/span\u003e]. According to the authors, this was a more frequent finding than the presence of scapular dyskinesis and limitation of active range of motion in painful shoulders.\u003c/p\u003e \u003c/div\u003e"},{"header":"9 Conclusion","content":"\u003cp\u003eThe present systematic review identified seven modifiable musculoskeletal factors among both athletic and nonathletic population groups. Decreased ER strength, a decreased ER:IR strength ratio, decreased IR, GIRD, ER gain, PMm shortness and scapular dyskinesis were associated with shoulder dysfunction. Modifiable musculoskeletal factors synthesized into several meta-analyses provided strong evidence for the presence of decreased ER strength, decreased ER:IR strength force couple ratios, decreased IR and GIRD being associated with shoulder dysfunction. Weaker evidence for the presence of a shortened PMm and scapular dyskinesis in the presence of shoulder dysfunction was determined. Regardless of the level of evidence, the presence of the abovementioned modifiable musculoskeletal factors was determined to be associated with shoulder dysfunction.\u003c/p\u003e \u003cp\u003e \u003cb\u003eRecommendations\u003c/b\u003e:\u003c/p\u003e \u003cp\u003eThe etiology of shoulder dysfunction is multifactorial and complex in nature. Early identification and correction of identified altered modifiable musculoskeletal factors have been shown to prevent the development of shoulder dysfunction in the current literature. All the identified modifiable musculoskeletal factors of the present systematic review should be considered in the comprehensive assessment and rehabilitation of the shoulder joint.\u003c/p\u003e \u003cp\u003eMoreover, correcting for the identified modifiable musculoskeletal factors, normalizing all the affected force\u0026ndash;couple ratios of the modifiable musculoskeletal factors and increasing the flexibility of identified modifiable musculoskeletal factors should lead to improved biomechanics of the scapulohumeral complex. This phenomenon is thought to be key in the rehabilitation process and should be monitored in all populations and not only in the athletic population.\u003c/p\u003e \u003cp\u003eEarly identification of biomechanical dysfunctions associated with any particular movement pattern of the shoulder can aid in preventing the development of shoulder pathology. A new evaluation model incorporating all the abovementioned modifiable musculoskeletal factors is therefore proposed.\u003c/p\u003e \u003cp\u003e \u003cb\u003eLimitations\u003c/b\u003e:\u003c/p\u003e \u003cp\u003eHowever, additional primary longitudinal studies should be conducted on the association between modifiable risk factors and the development of shoulder dysfunction. Due to the heterogeneity of the included primary studies, only a few studies reporting on the RR and OR could be pooled into a meta-analysis. Not all the included primary observational studies reported on RRs and ORs, and additional research in this area is needed. No data could be found on the role of the latissimus dorsi or the subscapularis in either primary observational or longitudinal studies or on the risk of developing shoulder dysfunction. However, even though the methodological quality of the studies included in this review was fair overall, namely, at levels 3 and 4, meaningful information was collected.\u003c/p\u003e"},{"header":"Declarations","content":"\u003ch2\u003eCompeting Interest:\u003c/h2\u003e\n\u003cp\u003eAll the authors certify that they have no affiliations with or involvement in any organization or entity with any financial interest or nonfinancial interest in the subject matter or materials discussed in this manuscript.\u003c/p\u003e\n\u003ch2\u003eFunding:\u003c/h2\u003e\n\u003cp\u003eNo funds, grants, or other support was received.\u003c/p\u003e\n\u003ch2\u003eAvailability of data:\u003c/h2\u003e\n\u003cp\u003eThe authors declare that the data supporting the findings of this study are available within the paper and in the supplementary online information files.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eDjade CD, Porgo TV, Zomahoun HT, Perrault- Sullivan G, Dionne CE (2020) Incidence of shoulder pain in 40 years old and over and associated factors: A systematic review. 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Rev Bras Fisioter 13(1):1\u0026ndash;9 PMID: 20411160; PMCID: PMC2857390\u003c/span\u003e\u003c/li\u003e \u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":true,"hideJournal":true,"highlight":"","institution":"University of the Witwatersrand","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"External, internal, strength, GIRD, Shouder dysfunction, strength ratios.","lastPublishedDoi":"10.21203/rs.3.rs-4555953/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-4555953/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003e\u003cstrong\u003eObjective:\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe objective of this systematic review of etiology and risk was to determine the association between modifiable musculoskeletal factors and shoulder dysfunction in an adult population.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eBackground:\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThere is still a paucity of evidence in the literature on shoulder function and the influence of modifiable musculoskeletal factors on function. The present study aimed to explore current and past research on all reported modifiable musculoskeletal factors to clarify the multifactorial etiology of shoulder dysfunction in an adult population.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eMethods:\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe methodology and meta-analysis process were performed as detailed in the JBI Reviewer’s Manual for Etiology and Risk, and the following guidelines were used according to the PRISMA (Preferred Items for Systematic Reviews and Meta-Analysis) statement. When a meta-analysis of the data was not possible, the SWiM (synthesis without meta-analysis) approach was used for the synthesis of pooled modifiable musculoskeletal factors. The outcome measure considered was shoulder dysfunction. The exposure parameters measured were modifiable musculoskeletal factors leading to the development of shoulder dysfunction. Patients aged between 18 and 75 years were included. A total of 7628 studies were identified worldwide through searching 12 databases. The results yielded by 91 studies were included in the systematic review. The risk of bias was low for 88 studies. Both females (2441) and males (3117) were included. The systematic review included cross-sectional and longitudinal studies investigating most sporting subpopulations (swimming, rugby, weightlifting, wheelchair, volleyball and baseball; 1003 participants) and members of the general population (4651). Pooling of the results into five meta-analyses was possible.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eResults:\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe results revealed that affected musculoskeletal factors led to a decrease in the strength of shoulder dysfunction during external rotation, with I\u003csup\u003e2\u003c/sup\u003e = 0 \u003csup\u003eindicating\u003c/sup\u003e a large positive effect size of 0.59 (p = 0.00), a decreased external versus internal muscle strength ratio, with I\u003csup\u003e2\u003c/sup\u003e = 46 indicating a large negative effect size of -0.69 (p = 0.002); decreased flexibility of the posterior capsule, with I \u003csup\u003e2\u003c/sup\u003e=0 indicating a small negative effect size of -0.0 (p = 0.45); decreased internal rotation, with a large negative effect size of -1.00 (p = 0); and a glenohumeral internal rotation deficit. Participants were 1.29 times more likely to develop shoulder dysfunction in the presence of decreased external rotation strength.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eDiscussion:\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eA comprehensive evaluation of the shoulder joint should include all identified musculoskeletal factors of the present systematic review at one point in time. Modifiable musculoskeletal factors include the strength of the external and internal rotators; the strength ratio of the external rotators: internal rotators; the internal rotation range of motion movement; the total range of motion; glenohumeral internal rotation deficit; pectoralis minor muscle length; posterior capsule and the glenohumeral posterior musculature flexibility; and scapular stabilizer strength and strength ratios.\u003c/p\u003e\n\u003cp\u003eThis protocol has been registered in PROSPERO (CRD 42021261719).\u003c/p\u003e","manuscriptTitle":"Modifiable musculoskeletal factors and their association with shoulder function in adults: A systematic review of risk and association","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2024-06-11 20:14:56","doi":"10.21203/rs.3.rs-4555953/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"47af4c75-d142-498f-98ce-220829a1ee6c","owner":[],"postedDate":"June 11th, 2024","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[{"id":33025424,"name":"Physical Medicine \u0026 Rehab"}],"tags":[],"updatedAt":"2024-06-11T20:14:57+00:00","versionOfRecord":[],"versionCreatedAt":"2024-06-11 20:14:56","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-4555953","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-4555953","identity":"rs-4555953","version":["v1"]},"buildId":"cBFmMYwuxLRRLfASyISRj","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}