Does having shorter tibias increase the likelihood of developing knee osteoarthritis? An observational cross-sectional radiographic analysis

Does having shorter tibias increase the likelihood of developing knee osteoarthritis? 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An observational cross-sectional radiographic analysis Xiaofeng Shi, Yibin Lu, Hongyu Chen, Xinlin Jia, Yuanqing Mao, and 1 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-4166157/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 Background The crural index, a fundamental property of the human skeletal system, is the ratio of the total length of the tibia to that of the femur. This study aimed to investigate the correlation between the crural index and knee osteoarthritis (OA). Methods This observational cross-sectional study included patients with preoperative weight-bearing full-length radiographs who were divided into two groups according to the Kellgren–Lawrence grading system. After rigorous screening based on the inclusion and exclusion criteria, 92 and 125 patients were included in the control and knee OA groups, respectively. The crural index, hip-knee-ankle angle (HKA), the deviation of the HKA from 180° (|HKA-180|), mechanical axis deflection (MAD), mechanical lateral distal femoral angle (mLDFA), medial proximal tibial angle (MPTA), arithmetic HKA (aHKA), and |aHKA| were compared between the two groups. In addition, linear regressions of the crural index were performed to assess their correlations. Results The crural index was significantly smaller in the knee OA group than in the control group (crural index: 79.49 ± 2.39 versus 82.14 ± 2.22, respectively; p < 0.001). The crural index correlated well with both |HKA-180| (R² = 0.54, p < 0.05) and MAD (R² = 0.57, p < 0.05). Conclusions Patients with OA of the knee have a much smaller crural index, which was closely related to the knee alignment. knee osteoarthritis the crural index knee alignment Figures Figure 1 Figure 2 Figure 3 Figure 4 Introduction Osteoarthritis (OA) is the most common joint disease worldwide, affecting approximately 10% of men and 18% of women over the age of 60 [ 1 ]. In particular, knee OA accounts for nearly four-fifths of global OA [ 2 ]. Because the pathogenesis of primary OA has not been elucidated, knee OA remains incurable. Therefore, an in-depth understanding of the factors that contribute to the development of knee OA can provide an effective strategy for its early prevention and treatment [ 3 ]. Our knowledge of the role of joint biomechanics in joints susceptible to OA is increasing through studies on large populations [ 2 ]. The influence of the tibial and femoral morphology on the development and progression of knee OA has also received increasing attention [ 4 , 5 ]. In addition, varus and valgus knee alignments increase the risk of OA development and progression in areas with high joint loading [ 6 – 8 ]. However, the crural index, a characteristic of the tibia and femur, has received little attention. The crural index is the ratio of the length of the lower leg to that of the thigh. In the skeleton, it is the ratio of the total length of the tibia to that of the femur in the natural position[ 9 ]. The crural index has frequently been used in previous archaeological, anthropological, and kinematic studies [ 10 – 12 ]. Anthropologists believe that different populations have different crural indices at different times, which have a profound effect on the kinematics and dynamics of human walking [ 13 ]. However, it is still unclear whether this index is associated with the onset and progression of knee osteoarthritis. This study aimed to explore the (1) difference in the crural index between individuals with and without knee OA and (2) correlation between the crural index and knee alignment. Methods Study Participants This observational cross-sectional study was approved by the Medical Ethics Committee (SH9H-2023-T257-1). Owing to the retrospective nature of the study, informed consent was not required. All the studies were conducted in accordance with the ethical standards of the Institutional Research Board and the Declaration of Helsinki and its subsequent amendments. Selection of Cases and Controls This was an observational cross-sectional radiographic study. The medical records and imaging data of consecutive patients with preoperative weight-bearing full-length radiographs from June 2021 to June 2023 at our center were collected. The control group included patients with Kellgren–Lawrence grades 0 and 1, and the knee OA group included patients with Kellgren–Lawrence grades 2, 3, and 4. The exclusion criteria for both groups were as follows: (1) inability to accurately measure femur and tibia lengths due to lower limb disease, including developmental congenital hip dysplasia, femoral head necrosis, and previous fracture; (2) unequal lengths of bilateral lower limbs that severely affect knee alignment, including pelvic tilt, scoliosis, and congenital lower limb developmental anomalies; (3) full-length radiographs in which the patella was not aligned in the anteroposterior projection with the center of the femoral condyles [ 14 ], which would interfere with alignment measurements; and (4) incomplete relevant medical records including age, height, and weight (Fig. 1 ). Measurement Medical records, including weight-bearing full-length radiographs, were extracted from the electronic medical record management system to determine the crural index and knee alignment as well as the patient's sex, age, height, and weight. In relevant studies, the femur bicondylar length (FBL) is mostly used as the femoral length in the crural index, whereas the tibia maximum length (TML) is generally used for the tibia [ 15 , 16 ]. Therefore, FBL is the distance from the uppermost part of the femoral head to the line connecting the lower surfaces of the distal medial and lateral condyles, and TML is the distance from the plane of the highest point of the proximal lateral tibial condyle to the plane of the lowest point of the medial malleolus, both of which were measured on weight-bearing full-length radiographs (Fig. 2 ). The hip-knee-ankle angle (HKA) was defined as the medial angle between the mechanical axes of the femur and tibia [ 17 ]. Mechanical axis deviation (MAD) was defined as the perpendicular distance from line a to the center of the knee joint (the soft tissue midpoint at the level of the knee joint space). The distal femoral mechanical angle (mLDFA) was defined as the lateral angle between the mechanical axis and knee joint line of the femur. The medial proximal tibial angle (MPTA) was defined as the medial angle between the mechanical axis and knee joint line of the tibia. To eliminate the difference in HKA between knee varus alignment and knee valgus alignment, we introduced the parameter |HKA-180|, which was the deviation of the HKA from 180°. Since during the development of OA, the joint cavity space narrows and the overall alignment (HKA) of the limb changes substantially, we obtained the knee alignment prior to the onset of arthritis by means of "arithmetic HKA" (aHKA) [ 18 , 19 ]. The aHKA was calculated by subtracting mLDFA from MPTA [ 19 ]. |aHKA| denotes the absolute value of aHKA. Two experienced radiologists performed two blinded measurements with an interval of > 2 weeks between measurements. Knee OA was evaluated radiologically and classified according to the Kellgren–Lawrence grading system by two experienced radiologists [ 20 ]. Statistical Analysis Differences between two groups of categorical data or measurements were tested using the chi-square test or independent samples Student's t-test, respectively. The consistency of radiologist Kellgren–Lawrence grading was assessed using weighted kappa, and the consistency of radiologist and intra-radiology measurements with other radiology measurements was assessed using intraclass correlation coefficients. To investigate whether there was a difference in the crural index between the knee OA and control groups, an independent samples t-test was used to compare the FBL, TML, and crural index between the two groups. Differences in knee alignment between the control and knee OA groups were compared using the independent samples t-test. To investigate whether knee alignment varied with the crural index, scatter plots were drawn for both groups using the crural index as the horizontal coordinate and HKA, |HKA-180|, MAD, mLDFA, MPTA, aHKA, and |aHKA| as the vertical coordinates. Correlations were assessed using Pearson’s correlation analysis. All statistical analyses were performed using the SPSS 22.0 software package and GraphPad Prism 9. Statistical significance was set at p < 0.05. Results Demographic Variables A total of 217 patients met the inclusion criteria, of whom 92 and 125 were included in the control and knee OA groups, respectively (Table 1 ). The consistency of the inter-radiologist Kellgren–Lawrence grading (weighted kappa = 0.868, p < 0.05), inter-radiologist measurements (intraclass correlation coefficient = 0.989, p < 0.05), and intra-radiologist measurements (intraclass correlation coefficient = 0.994, p < 0.05) were excellent. Table 1 Comparisons of patient demographics between the control and knee OA groups Variables The Control Group(n = 92) The Knee OA Group(n = 125) P-Value Mean age in years (range) 66.09(45–90) 67.89(34–82) 0.213 Sex (% women) 60(65.22%)༉ 82(65.60%) 0.93 Mean BMI (range) 24.20(18.36–31.56) 25.08(17.88–36.05) 0.063 BMI, body mass index; OA, osteoarthritis; Difference in the crural index between the control and knee OA groups The TML and crural index in the knee OA group were 33.84 and 79.49, respectively, which were significantly lower than those of the control group (35.16 and 82.14, respectively; both, p 0.05) (Table 2 ). Table 2 Comparisons of TML, FBL and the crural index between the control and knee OA groups Variables The Control Group(n = 92) The Knee OA Group(n = 125) P-Value Tibia Maximum Length (mm) 35.16 ± 2.37 33.84 ± 2.35 <0.001 Femur Bicondylar Length (mm) 42.81 ± 2.73 42.57 ± 2.68 0.507 The Crural Index 82.14 ± 2.22 79.49 ± 2.39 <0.001 Values are presented as mean ± standard deviation. Correlation of the crural index and knee alignment The HKA, |HKA-180|, MAD, mLDFA, MPTA, aHKA, and |aHKA| were significantly different between the two groups (p < 0.05 for all comparisons), and the knee OA group had poorer knee alignment than the control group (knee OA group vs. control group, 174.93 vs. 178.69°; p < 0.05). The difference in |HKA-180| between the two groups was more significant (knee OA group vs. control group, 7.37 vs. 2.76; p < 0.05) (Table 3 ). Table 3 Comparisons of the knee alignment between the control and knee OA groups. Variables The Control Group(n = 92) The Knee OA Group(n = 125) P-Value HKA(°) 178.69 ± 3.15 174.93 ± 6.45 <0.001 |HKA-180|(°) 2.76 ± 1.99 7.37 ± 3.59 <0.001 MAD(mm) 9.26 ± 7.36 24.74 ± 11.25 <0.001 mLDFA(°) 87.36 ± 2.41 88.73 ± 3.17 <0.001 MPTA(°) 88.26 ± 2.33 87.00 ± 2.68 <0.001 aHKA(°) 0.89 ± 2.58 -1.73 ± 4.35 <0.001 |aHKA| 2.13 ± 1.71 3.73 ± 2.81 <0.001 Values are presented as mean ± standard deviation The crural index and HKA were moderately correlated in 217 patients (R² = 0.20; 95% confidence interval [CI], 0.70 to 1.20; p < 0.05). However, the correlation between the crural index and |HKA-180| was excellent (R² = 0.54; 95% CI, -1.17 to -0.91; p < 0.05). The correlation between the crural index and MAD was also very good (R² = 0.57; 95% CI, -3.94 to -3.11; p < 0.05). Moreover, the crural index was correlated with aHKA (R² = 0.15; 95% CI, 0.39 to 0.75; p < 0.05) and |aHKA| (R² = 0.13; 95% CI, -0.46 to -0.22; p < 0.05). However, there was no significant correlation between the crural index and other parameters, including mLDFA (R² = 0.06; 95% CI, -0.41 to -0.12; p < 0.05) and MPTA (R² = 0.10; 95% CI, 0.18 to 0.43; p < 0.05) (Fig. 3 ). We then performed separate linear regressions for the correlation of varus and valgus with the crural index. The correlation between varus and the crural index was better than that between valgus and the crural index (HKA-R²: 0.57 vs. 0.36, respectively, both p<0.05; |HKA-180|-R²: 0.57 vs. 0.36, respectively, both p<0.05; MAD-R²: 0.61 vs. 0.39, respectively, both p<0.05; mLDFA-R²: 0.13 vs. 0.09, respectively, both p<0.05; MPTA-R²: 0.09 vs. 0.03, p<0.05 vs. p = 0.2474, respectively; aHKA-R²: 0.08 vs. 0.04, p<0.05 vs. p = 0.1827, respectively; |aHKA|-R²: 0.20 vs. 0.05, p<0.05 vs. p = 0.1165, respectively) (Fig. 4 ). Discussion The crural index of patients with knee OA was significantly lower than that of healthy individuals. In addition, the smaller the crural index, the poorer the alignment of the knee joint. Although the degradation of cartilage and subchondral bone may slightly affect the measurement of length, particularly in severe cases of subchondral bone wear, the impact is usually minimal - often just a few millimeters. Consequently, joint degeneration does not significantly alter the length of the femur and tibia or their ratio, known as the crural index. This can thus be considered a consistent skeletal feature. In our study, we found that the crural index was much smaller in the knee OA group than in the control group (p < 0.001). A comparison of FBL and TML indicated that the smaller index was mainly due to the shorter tibia (p < 0.001); no significant difference in FBL (p = 0.507) was observed between the two groups. The knee alignment was also significantly correlated with the crural index. Poor knee alignment includes both varus and valgus [ 21 , 22 ], therefore, the HKA does not fully capture knee misalignment. Here, we included |HKA-180| and performed a linear regression with the crural index. The knee misalignment was more significant in the knee OA group than in the control group (HKA-R² vs. |HKA-180|- R² = 0.20 vs. 0.54, both p < 0.05). In addition, the results of the linear regression showed that the smaller the index, the larger the MAD. During the process of knee OA, the overall alignment of the limb (HKA) changes significantly over time due to the narrowing of the joint cavity space, and in the absence of arthritic bone defects at the central compartmental contact points, the deformed alignment of the lower limb can be determined by aHKA [ 23 ]. Therefore, to determine the relationship between the crural index and knee alignment before the onset of OA, we performed a linear regression between the crural index and aHKA. Our findings reveal a relatively strong correlation between the crural index and aHKA (R² = 0.15; p < 0.05). This suggests that the crural index may play a role in the development of knee OA. These findings indicate that the smaller the crural index, the more likely the knee alignment is to be poor. A smaller index indicates that the femur, as opposed to the tibia, as a greater moment, increases the rotation centered on the knee joint, thereby increasing the offset of knee alignment [ 24 ]. However, more precise biomechanical analysis is required to validate this finding. For the correlation between the crural index and knee OA, we thought that smaller indices were usually more likely to lead to the development of knee OA. This is consistent with the findings of previous studies, which stated that individuals with a higher femur length-to-height ratio (smaller crural index) were more likely to suffer from knee OA [ 25 ]. This could possibly be attributed to the tendency of smaller indices to result in suboptimal knee alignment, and lower extremity alignment is strongly associated with knee OA [ 6 , 7 ]. Varus deformities and medial compartmental knee OA often promote each other, and valgus deformities and lateral compartment OA also have a mutually promoting relationship. In addition, gait is closely related to the development of knee OA [ 26 , 27 ], and the crural index has a profound effect on the kinematics and kinetics of human walking [ 13 ]. Exploring the differences in the prevalence and incidence of knee OA by age, sex, and region will help us better understand the underlying causes of knee OA [28]. The prevalence and incidence of knee OA show significant differences not only in terms of sex but also by regional distribution. At the continental level, the prevalence in Asia (19.2%) is much higher than that in Europe (13.4%) and North America (15.8%). Some representative countries, such as Japan, have a prevalence of 525/10,000 person-years, which is also much higher than that of the United States (130/10,000 person-years) and the United Kingdom (315/10,000 person-years) [ 29 ]. Moreover, the cause of this phenomenon remains unknown. Here, we focus on the crural index as an influencing factor, which may be one of the reasons. The crural index in East Asia, represented by China and Japan, is usually less than 0.83 and is known as the short tibia type, whereas the crural index in the United States and Australia is usually greater than 0.83 and is known as the long tibia type [ 30 ]. In addition, the crural index in females is usually lower than that in males [ 31 ]. Therefore, we believe that the crural index, a less studied factor, may be a potential factor in the development of knee OA. This study had some limitations. First, because this was a single-center retrospective cross-sectional study, we were unable to thoroughly clarify the causal relationship between the crural index and knee OA. Additionally, the sample was relatively homogeneous and lacked generalizability, as most patients were female and Asian. Furthermore, the crural index differed among different races[ 30 ]; therefore, caution should be exercised when applying the results of this study to other groups. However, given the multitude of factors influencing OA, it's improbable for one single factor to have an excessively high impact. The correlation coefficients we've obtained suggest that the crural index is indeed an important parameter, despite the complex interplay of contributing factors to OA. In conclusion, our findings indicate a close association between the crural index, knee OA, and knee alignment. Consequently, we propose that the crural index should be recognized as a risk factor for knee OA, warranting further consideration in preventive treatments and more comprehensive studies. Abbreviations OA Osteoarthritis HKA Hip-knee-ankle angle MAD Mechanical axis deflection mLDFA Mechanical lateral distal femoral angle MPTA Medial proximal tibial angle aHKA Arithmetic hip-knee-ankle angle FBL Femur bicondylar length TML Tibia maximum length Declarations Availability of data and materials Can be requested from the corresponding author Funding This study has received funding by Shanghai "Rising Stars of Medical Talent" Youth Development Program, Youth Medical Talents-Specialist Program, (SHHWRS 2023-62) and National Natural Science Foundation of China (Grant No. 31900941). Conflict of Interest: The authors of this manuscript declare no relationships with any companies, whose products or services may be related to the subject matter of the article. Statistics and Biometry: No complex statistical methods were necessary for this paper. Informed Consent: Written informed consent was not required for this study because the biological information and data of the imaging data used in the study have been de-labelled, which meant they were not individually identifiable and traceable. Exemption from obtaining the informed consent of the subject would not have a negative impact on the rights and interests of the subject. Ethical Approval: This observational cross-sectional study was approved by the Medical Ethics Committee (SH9H-2023-T257-1). The biological information and imaging data used in the study have been anonymised, which means they are not individually identifiable or traceable. Exemption from obtaining informed consent from the subjects will not have a negative impact on the rights or interests of the subjects. Author Contribution Xiaofeng Shi: Conceptualization, Methodology, Data curation, Investigation, Writing – original draft.Yibin Lu: Methodology, Investigation, Writing – original draft.Hongyu Chen:Methodology, Formal analysis.Xinlin Jia: Data curation, literature review.YuanQing Mao: Project administration, Supervision.Jingwei Zhang: Writing – review & editing, Supervision, Project administration, Funding acquisition. References Glyn-Jones S, Palmer AJ, Agricola R, London et al. England), 386(9991), 376–87. Martel-Pelletier J, Barr AJ, Cicuttini FM et al. (2016). Osteoarthritis. Nature reviews. Disease primers, 2, 16072. Mahmoudian A, Lohmander LS, Mobasheri A, et al. Early-stage symptomatic osteoarthritis of the knee — time for action. Nat Rev Rheumatol. 2021;17:621–32. Neogi T, Bowes MA, Niu J, et al. Magnetic resonance imaging-based three-dimensional bone shape of the knee predicts onset of knee osteoarthritis: data from the osteoarthritis initiative. 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The effects of shoe-worn insoles on gait biomechanics in people with knee osteoarthritis: a systematic review and meta-analysis. Br J Sports Med. 2018;52(4):238–53. L. Safiri S, Kolahi AA, Smith E, et al. Global, regional and national burden of osteoarthritis 1990–2017: a systematic analysis of the Global Burden of Disease Study 2017. Ann Rheum Dis. 2020;79(6):819–28. Cui A, Li H, Wang D, Zhong J, Chen Y, Lu H. ( 2020). Global, regional prevalence, incidence and risk factors of knee osteoarthritis in population-based studies. EClinicalMedicine, 29–30, 100587. Auerbach BM, Ruff CB. Stature estimation formulae for indigenous North American populations. Am J Phys Anthropol. 2010;141(2):190–207. Nuger RL. (2009). Sex differences in brachial and crural indices in relation to climate. Am J Phys Anthropol, 200–1. Additional Declarations No competing interests reported. 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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-4166157","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":285637565,"identity":"76e5b4df-5edf-49f2-8889-a637e88bea9d","order_by":0,"name":"Xiaofeng Shi","email":"","orcid":"","institution":"Shanghai Ninth People's Hospital","correspondingAuthor":false,"prefix":"","firstName":"Xiaofeng","middleName":"","lastName":"Shi","suffix":""},{"id":285637566,"identity":"ba3dbdcc-bba0-4f05-9140-85a967776bde","order_by":1,"name":"Yibin Lu","email":"","orcid":"","institution":"Shanghai Ninth People's Hospital","correspondingAuthor":false,"prefix":"","firstName":"Yibin","middleName":"","lastName":"Lu","suffix":""},{"id":285637567,"identity":"1a67cd1a-6da3-454e-a72b-a5c5c11c9076","order_by":2,"name":"Hongyu Chen","email":"","orcid":"","institution":"Shanghai Ninth People's Hospital","correspondingAuthor":false,"prefix":"","firstName":"Hongyu","middleName":"","lastName":"Chen","suffix":""},{"id":285637568,"identity":"ce672111-9b37-4419-824b-d1c07216d583","order_by":3,"name":"Xinlin Jia","email":"","orcid":"","institution":"Shanghai Ninth People's Hospital","correspondingAuthor":false,"prefix":"","firstName":"Xinlin","middleName":"","lastName":"Jia","suffix":""},{"id":285637569,"identity":"2b48eb0b-b0b0-4340-9802-0ebfca3d819a","order_by":4,"name":"Yuanqing Mao","email":"","orcid":"","institution":"Shanghai Ninth People's Hospital","correspondingAuthor":false,"prefix":"","firstName":"Yuanqing","middleName":"","lastName":"Mao","suffix":""},{"id":285637570,"identity":"42efb951-8589-469e-9c8a-7da5966acaaa","order_by":5,"name":"Jingwei Zhang","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAAtElEQVRIiWNgGAWjYFCCAyDChoefv4E0LWkykjMOkGbVYRuDhgQi1co3njFg5vlznseA4QDjh485RGhhbABq4W27zWPO3MAsOXMbEVqYGc5uYOZtuM1j2XCAjZmXGC1sIC08f87xGBxIIFILD1gL2wEStEgwnP/AOLctmUdyxsFm4vwiP+NYAsObP3b2/PzNBz98JEYLg8QB9l88YBZjAzHqgQCYThh/EKl2FIyCUTAKRigAAL2xNH5yOnaQAAAAAElFTkSuQmCC","orcid":"","institution":"Shanghai Ninth People's Hospital","correspondingAuthor":true,"prefix":"","firstName":"Jingwei","middleName":"","lastName":"Zhang","suffix":""}],"badges":[],"createdAt":"2024-03-26 01:27:36","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-4166157/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-4166157/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":53964566,"identity":"4452e619-5d4c-425f-930e-c71a423f9e96","added_by":"auto","created_at":"2024-04-02 19:01:43","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":185800,"visible":true,"origin":"","legend":"\u003cp\u003ePatient recruitment and group establishment flowchart.\u003c/p\u003e","description":"","filename":"OnlineFigure12.png","url":"https://assets-eu.researchsquare.com/files/rs-4166157/v1/b2484f0e3e33f7807cf3897d.png"},{"id":53964756,"identity":"12fcd368-1b95-42ce-a083-d512f5f7ede4","added_by":"auto","created_at":"2024-04-02 19:09:43","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":249542,"visible":true,"origin":"","legend":"\u003cp\u003eMeasurements of the FBL and TML. The crural index = TML*100 / FBL.\u003c/p\u003e","description":"","filename":"OnlineFigure2.png","url":"https://assets-eu.researchsquare.com/files/rs-4166157/v1/98ae6184cdd270047d57ab87.png"},{"id":53964568,"identity":"5de36b52-30cb-4695-bd43-c2a1dd84e49a","added_by":"auto","created_at":"2024-04-02 19:01:43","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":135301,"visible":true,"origin":"","legend":"\u003cp\u003eRelationship between the knee alignment and crural index.\u003c/p\u003e","description":"","filename":"OnlineFigure3.png","url":"https://assets-eu.researchsquare.com/files/rs-4166157/v1/4b5d8f7fc3ca9f0c143099c4.png"},{"id":53964570,"identity":"392fdc00-e4cc-4547-8aab-15c0af91140c","added_by":"auto","created_at":"2024-04-02 19:01:43","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":151009,"visible":true,"origin":"","legend":"\u003cp\u003eRelationship between the knee alignment and the crural index in varus or valgus.\u003c/p\u003e","description":"","filename":"OnlineFigure4.png","url":"https://assets-eu.researchsquare.com/files/rs-4166157/v1/b6874b3760f8bcab46ad1185.png"},{"id":54772786,"identity":"f0be3ed4-0830-4554-82ce-c63a0c190602","added_by":"auto","created_at":"2024-04-16 14:45:10","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1265113,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-4166157/v1/832386b4-0aa5-491e-ba5c-97a567cd046e.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Does having shorter tibias increase the likelihood of developing knee osteoarthritis? An observational cross-sectional radiographic analysis","fulltext":[{"header":"Introduction","content":"\u003cp\u003eOsteoarthritis (OA) is the most common joint disease worldwide, affecting approximately 10% of men and 18% of women over the age of 60 [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e]. In particular, knee OA accounts for nearly four-fifths of global OA [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]. Because the pathogenesis of primary OA has not been elucidated, knee OA remains incurable. Therefore, an in-depth understanding of the factors that contribute to the development of knee OA can provide an effective strategy for its early prevention and treatment [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eOur knowledge of the role of joint biomechanics in joints susceptible to OA is increasing through studies on large populations [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]. The influence of the tibial and femoral morphology on the development and progression of knee OA has also received increasing attention [\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e, \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e]. In addition, varus and valgus knee alignments increase the risk of OA development and progression in areas with high joint loading [\u003cspan additionalcitationids=\"CR7\" citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e]. However, the crural index, a characteristic of the tibia and femur, has received little attention.\u003c/p\u003e \u003cp\u003eThe crural index is the ratio of the length of the lower leg to that of the thigh. In the skeleton, it is the ratio of the total length of the tibia to that of the femur in the natural position[\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e]. The crural index has frequently been used in previous archaeological, anthropological, and kinematic studies [\u003cspan additionalcitationids=\"CR11\" citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e]. Anthropologists believe that different populations have different crural indices at different times, which have a profound effect on the kinematics and dynamics of human walking [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e]. However, it is still unclear whether this index is associated with the onset and progression of knee osteoarthritis.\u003c/p\u003e \u003cp\u003eThis study aimed to explore the (1) difference in the crural index between individuals with and without knee OA and (2) correlation between the crural index and knee alignment.\u003c/p\u003e"},{"header":"Methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003eStudy Participants\u003c/h2\u003e \u003cp\u003eThis observational cross-sectional study was approved by the Medical Ethics Committee (SH9H-2023-T257-1). Owing to the retrospective nature of the study, informed consent was not required. All the studies were conducted in accordance with the ethical standards of the Institutional Research Board and the Declaration of Helsinki and its subsequent amendments.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec4\" class=\"Section2\"\u003e \u003ch2\u003eSelection of Cases and Controls\u003c/h2\u003e \u003cp\u003eThis was an observational cross-sectional radiographic study. The medical records and imaging data of consecutive patients with preoperative weight-bearing full-length radiographs from June 2021 to June 2023 at our center were collected. The control group included patients with Kellgren\u0026ndash;Lawrence grades 0 and 1, and the knee OA group included patients with Kellgren\u0026ndash;Lawrence grades 2, 3, and 4. The exclusion criteria for both groups were as follows: (1) inability to accurately measure femur and tibia lengths due to lower limb disease, including developmental congenital hip dysplasia, femoral head necrosis, and previous fracture; (2) unequal lengths of bilateral lower limbs that severely affect knee alignment, including pelvic tilt, scoliosis, and congenital lower limb developmental anomalies; (3) full-length radiographs in which the patella was not aligned in the anteroposterior projection with the center of the femoral condyles [\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e], which would interfere with alignment measurements; and (4) incomplete relevant medical records including age, height, and weight (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec5\" class=\"Section2\"\u003e \u003ch2\u003eMeasurement\u003c/h2\u003e \u003cp\u003eMedical records, including weight-bearing full-length radiographs, were extracted from the electronic medical record management system to determine the crural index and knee alignment as well as the patient's sex, age, height, and weight. In relevant studies, the femur bicondylar length (FBL) is mostly used as the femoral length in the crural index, whereas the tibia maximum length (TML) is generally used for the tibia [\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e, \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e]. Therefore, FBL is the distance from the uppermost part of the femoral head to the line connecting the lower surfaces of the distal medial and lateral condyles, and TML is the distance from the plane of the highest point of the proximal lateral tibial condyle to the plane of the lowest point of the medial malleolus, both of which were measured on weight-bearing full-length radiographs (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e). The hip-knee-ankle angle (HKA) was defined as the medial angle between the mechanical axes of the femur and tibia [\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e]. Mechanical axis deviation (MAD) was defined as the perpendicular distance from line a to the center of the knee joint (the soft tissue midpoint at the level of the knee joint space). The distal femoral mechanical angle (mLDFA) was defined as the lateral angle between the mechanical axis and knee joint line of the femur. The medial proximal tibial angle (MPTA) was defined as the medial angle between the mechanical axis and knee joint line of the tibia. To eliminate the difference in HKA between knee varus alignment and knee valgus alignment, we introduced the parameter |HKA-180|, which was the deviation of the HKA from 180\u0026deg;. Since during the development of OA, the joint cavity space narrows and the overall alignment (HKA) of the limb changes substantially, we obtained the knee alignment prior to the onset of arthritis by means of \"arithmetic HKA\" (aHKA) [\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e, \u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e]. The aHKA was calculated by subtracting mLDFA from MPTA [\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e]. |aHKA| denotes the absolute value of aHKA. Two experienced radiologists performed two blinded measurements with an interval of \u0026gt;\u0026thinsp;2 weeks between measurements. Knee OA was evaluated radiologically and classified according to the Kellgren\u0026ndash;Lawrence grading system by two experienced radiologists [\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e].\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec6\" class=\"Section2\"\u003e \u003ch2\u003eStatistical Analysis\u003c/h2\u003e \u003cp\u003eDifferences between two groups of categorical data or measurements were tested using the chi-square test or independent samples Student's t-test, respectively. The consistency of radiologist Kellgren\u0026ndash;Lawrence grading was assessed using weighted kappa, and the consistency of radiologist and intra-radiology measurements with other radiology measurements was assessed using intraclass correlation coefficients. To investigate whether there was a difference in the crural index between the knee OA and control groups, an independent samples t-test was used to compare the FBL, TML, and crural index between the two groups. Differences in knee alignment between the control and knee OA groups were compared using the independent samples t-test. To investigate whether knee alignment varied with the crural index, scatter plots were drawn for both groups using the crural index as the horizontal coordinate and HKA, |HKA-180|, MAD, mLDFA, MPTA, aHKA, and |aHKA| as the vertical coordinates. Correlations were assessed using Pearson\u0026rsquo;s correlation analysis. All statistical analyses were performed using the SPSS 22.0 software package and GraphPad Prism 9. Statistical significance was set at p\u0026thinsp;\u0026lt;\u0026thinsp;0.05.\u003c/p\u003e \u003c/div\u003e"},{"header":"Results","content":"\u003cdiv id=\"Sec8\" class=\"Section2\"\u003e \u003ch2\u003eDemographic Variables\u003c/h2\u003e \u003cp\u003eA total of 217 patients met the inclusion criteria, of whom 92 and 125 were included in the control and knee OA groups, respectively (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). The consistency of the inter-radiologist Kellgren\u0026ndash;Lawrence grading (weighted kappa\u0026thinsp;=\u0026thinsp;0.868, p\u0026thinsp;\u0026lt;\u0026thinsp;0.05), inter-radiologist measurements (intraclass correlation coefficient\u0026thinsp;=\u0026thinsp;0.989, p\u0026thinsp;\u0026lt;\u0026thinsp;0.05), and intra-radiologist measurements (intraclass correlation coefficient\u0026thinsp;=\u0026thinsp;0.994, p\u0026thinsp;\u0026lt;\u0026thinsp;0.05) were excellent.\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\u003eComparisons of patient demographics between the control and knee OA groups\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"4\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eVariables\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eThe Control Group(n\u0026thinsp;=\u0026thinsp;92)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eThe Knee OA Group(n\u0026thinsp;=\u0026thinsp;125)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eP-Value\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMean age in years (range)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e66.09(45\u0026ndash;90)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e67.89(34\u0026ndash;82)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.213\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSex (% women)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e60(65.22%)༉\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e82(65.60%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.93\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMean BMI (range)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e24.20(18.36\u0026ndash;31.56)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e25.08(17.88\u0026ndash;36.05)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.063\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003ctfoot\u003e \u003ctr\u003e\u003ctd colspan=\"4\"\u003eBMI, body mass index; OA, osteoarthritis;\u003c/td\u003e\u003c/tr\u003e \u003c/tfoot\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec9\" class=\"Section2\"\u003e \u003ch2\u003eDifference in the crural index between the control and knee OA groups\u003c/h2\u003e \u003cp\u003eThe TML and crural index in the knee OA group were 33.84 and 79.49, respectively, which were significantly lower than those of the control group (35.16 and 82.14, respectively; both, p\u0026thinsp;\u0026lt;\u0026thinsp;0.05). However, there was no significant difference in FBL (p\u0026thinsp;\u0026gt;\u0026thinsp;0.05) (Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eComparisons of TML, FBL and the crural index between the control and knee OA groups\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"4\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\"\u0026plusmn;\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\"\u0026plusmn;\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eVariables\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eThe Control Group(n\u0026thinsp;=\u0026thinsp;92)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eThe Knee OA Group(n\u0026thinsp;=\u0026thinsp;125)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eP-Value\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eTibia Maximum Length (mm)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e \u003cp\u003e35.16\u0026thinsp;\u0026plusmn;\u0026thinsp;2.37\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e33.84\u0026thinsp;\u0026plusmn;\u0026thinsp;2.35\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e\u0026lt;0.001\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eFemur Bicondylar Length (mm)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e \u003cp\u003e42.81\u0026thinsp;\u0026plusmn;\u0026thinsp;2.73\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e42.57\u0026thinsp;\u0026plusmn;\u0026thinsp;2.68\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.507\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eThe Crural Index\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e \u003cp\u003e82.14\u0026thinsp;\u0026plusmn;\u0026thinsp;2.22\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e79.49\u0026thinsp;\u0026plusmn;\u0026thinsp;2.39\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e\u0026lt;0.001\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003ctfoot\u003e \u003ctr\u003e\u003ctd colspan=\"4\"\u003eValues are presented as mean\u0026thinsp;\u0026plusmn;\u0026thinsp;standard deviation.\u003c/td\u003e\u003c/tr\u003e \u003c/tfoot\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec10\" class=\"Section2\"\u003e \u003ch2\u003eCorrelation of the crural index and knee alignment\u003c/h2\u003e \u003cp\u003eThe HKA, |HKA-180|, MAD, mLDFA, MPTA, aHKA, and |aHKA| were significantly different between the two groups (p\u0026thinsp;\u0026lt;\u0026thinsp;0.05 for all comparisons), and the knee OA group had poorer knee alignment than the control group (knee OA group vs. control group, 174.93 vs. 178.69\u0026deg;; p\u0026thinsp;\u0026lt;\u0026thinsp;0.05). The difference in |HKA-180| between the two groups was more significant (knee OA group vs. control group, 7.37 vs. 2.76; p\u0026thinsp;\u0026lt;\u0026thinsp;0.05) (Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab3\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 3\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eComparisons of the knee alignment between the control and knee OA groups.\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"4\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\"\u0026plusmn;\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\"\u0026plusmn;\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eVariables\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eThe Control Group(n\u0026thinsp;=\u0026thinsp;92)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eThe Knee OA Group(n\u0026thinsp;=\u0026thinsp;125)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eP-Value\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eHKA(\u0026deg;)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e \u003cp\u003e178.69\u0026thinsp;\u0026plusmn;\u0026thinsp;3.15\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e174.93\u0026thinsp;\u0026plusmn;\u0026thinsp;6.45\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e\u0026lt;0.001\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e|HKA-180|(\u0026deg;)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e \u003cp\u003e2.76\u0026thinsp;\u0026plusmn;\u0026thinsp;1.99\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e7.37\u0026thinsp;\u0026plusmn;\u0026thinsp;3.59\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e\u0026lt;0.001\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMAD(mm)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e \u003cp\u003e9.26\u0026thinsp;\u0026plusmn;\u0026thinsp;7.36\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e24.74\u0026thinsp;\u0026plusmn;\u0026thinsp;11.25\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e\u0026lt;0.001\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003emLDFA(\u0026deg;)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e \u003cp\u003e87.36\u0026thinsp;\u0026plusmn;\u0026thinsp;2.41\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e88.73\u0026thinsp;\u0026plusmn;\u0026thinsp;3.17\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e\u0026lt;0.001\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMPTA(\u0026deg;)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e \u003cp\u003e88.26\u0026thinsp;\u0026plusmn;\u0026thinsp;2.33\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e87.00\u0026thinsp;\u0026plusmn;\u0026thinsp;2.68\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e\u0026lt;0.001\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eaHKA(\u0026deg;)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e \u003cp\u003e0.89\u0026thinsp;\u0026plusmn;\u0026thinsp;2.58\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e-1.73\u0026thinsp;\u0026plusmn;\u0026thinsp;4.35\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e\u0026lt;0.001\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e|aHKA|\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e \u003cp\u003e2.13\u0026thinsp;\u0026plusmn;\u0026thinsp;1.71\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e3.73\u0026thinsp;\u0026plusmn;\u0026thinsp;2.81\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e\u0026lt;0.001\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003ctfoot\u003e \u003ctr\u003e\u003ctd colspan=\"4\"\u003eValues are presented as mean\u0026thinsp;\u0026plusmn;\u0026thinsp;standard deviation\u003c/td\u003e\u003c/tr\u003e \u003c/tfoot\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eThe crural index and HKA were moderately correlated in 217 patients (R\u0026sup2; = 0.20; 95% confidence interval [CI], 0.70 to 1.20; p\u0026thinsp;\u0026lt;\u0026thinsp;0.05). However, the correlation between the crural index and |HKA-180| was excellent (R\u0026sup2; = 0.54; 95% CI, -1.17 to -0.91; p\u0026thinsp;\u0026lt;\u0026thinsp;0.05). The correlation between the crural index and MAD was also very good (R\u0026sup2; = 0.57; 95% CI, -3.94 to -3.11; p\u0026thinsp;\u0026lt;\u0026thinsp;0.05). Moreover, the crural index was correlated with aHKA (R\u0026sup2; = 0.15; 95% CI, 0.39 to 0.75; p\u0026thinsp;\u0026lt;\u0026thinsp;0.05) and |aHKA| (R\u0026sup2; = 0.13; 95% CI, -0.46 to -0.22; p\u0026thinsp;\u0026lt;\u0026thinsp;0.05). However, there was no significant correlation between the crural index and other parameters, including mLDFA (R\u0026sup2; = 0.06; 95% CI, -0.41 to -0.12; p\u0026thinsp;\u0026lt;\u0026thinsp;0.05) and MPTA (R\u0026sup2; = 0.10; 95% CI, 0.18 to 0.43; p\u0026thinsp;\u0026lt;\u0026thinsp;0.05) (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eWe then performed separate linear regressions for the correlation of varus and valgus with the crural index. The correlation between varus and the crural index was better than that between valgus and the crural index (HKA-R\u0026sup2;: 0.57 vs. 0.36, respectively, both p\u0026lt;0.05; |HKA-180|-R\u0026sup2;: 0.57 vs. 0.36, respectively, both p\u0026lt;0.05; MAD-R\u0026sup2;: 0.61 vs. 0.39, respectively, both p\u0026lt;0.05; mLDFA-R\u0026sup2;: 0.13 vs. 0.09, respectively, both p\u0026lt;0.05; MPTA-R\u0026sup2;: 0.09 vs. 0.03, p\u0026lt;0.05 vs. p\u0026thinsp;=\u0026thinsp;0.2474, respectively; aHKA-R\u0026sup2;: 0.08 vs. 0.04, p\u0026lt;0.05 vs. p\u0026thinsp;=\u0026thinsp;0.1827, respectively; |aHKA|-R\u0026sup2;: 0.20 vs. 0.05, p\u0026lt;0.05 vs. p\u0026thinsp;=\u0026thinsp;0.1165, respectively) (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e"},{"header":"Discussion","content":"\u003cp\u003eThe crural index of patients with knee OA was significantly lower than that of healthy individuals. In addition, the smaller the crural index, the poorer the alignment of the knee joint. Although the degradation of cartilage and subchondral bone may slightly affect the measurement of length, particularly in severe cases of subchondral bone wear, the impact is usually minimal - often just a few millimeters. Consequently, joint degeneration does not significantly alter the length of the femur and tibia or their ratio, known as the crural index. This can thus be considered a consistent skeletal feature. In our study, we found that the crural index was much smaller in the knee OA group than in the control group (p\u0026thinsp;\u0026lt;\u0026thinsp;0.001). A comparison of FBL and TML indicated that the smaller index was mainly due to the shorter tibia (p\u0026thinsp;\u0026lt;\u0026thinsp;0.001); no significant difference in FBL (p\u0026thinsp;=\u0026thinsp;0.507) was observed between the two groups.\u003c/p\u003e \u003cp\u003eThe knee alignment was also significantly correlated with the crural index. Poor knee alignment includes both varus and valgus [\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e, \u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e], therefore, the HKA does not fully capture knee misalignment. Here, we included |HKA-180| and performed a linear regression with the crural index. The knee misalignment was more significant in the knee OA group than in the control group (HKA-R\u0026sup2; vs. |HKA-180|- R\u0026sup2; = 0.20 vs. 0.54, both p\u0026thinsp;\u0026lt;\u0026thinsp;0.05). In addition, the results of the linear regression showed that the smaller the index, the larger the MAD. During the process of knee OA, the overall alignment of the limb (HKA) changes significantly over time due to the narrowing of the joint cavity space, and in the absence of arthritic bone defects at the central compartmental contact points, the deformed alignment of the lower limb can be determined by aHKA [\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e]. Therefore, to determine the relationship between the crural index and knee alignment before the onset of OA, we performed a linear regression between the crural index and aHKA. Our findings reveal a relatively strong correlation between the crural index and aHKA (R\u0026sup2; = 0.15; p\u0026thinsp;\u0026lt;\u0026thinsp;0.05). This suggests that the crural index may play a role in the development of knee OA. These findings indicate that the smaller the crural index, the more likely the knee alignment is to be poor. A smaller index indicates that the femur, as opposed to the tibia, as a greater moment, increases the rotation centered on the knee joint, thereby increasing the offset of knee alignment [\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e]. However, more precise biomechanical analysis is required to validate this finding.\u003c/p\u003e \u003cp\u003eFor the correlation between the crural index and knee OA, we thought that smaller indices were usually more likely to lead to the development of knee OA. This is consistent with the findings of previous studies, which stated that individuals with a higher femur length-to-height ratio (smaller crural index) were more likely to suffer from knee OA [\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e]. This could possibly be attributed to the tendency of smaller indices to result in suboptimal knee alignment, and lower extremity alignment is strongly associated with knee OA [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e, \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e]. Varus deformities and medial compartmental knee OA often promote each other, and valgus deformities and lateral compartment OA also have a mutually promoting relationship. In addition, gait is closely related to the development of knee OA [\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e, \u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e], and the crural index has a profound effect on the kinematics and kinetics of human walking [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eExploring the differences in the prevalence and incidence of knee OA by age, sex, and region will help us better understand the underlying causes of knee OA [28]. The prevalence and incidence of knee OA show significant differences not only in terms of sex but also by regional distribution. At the continental level, the prevalence in Asia (19.2%) is much higher than that in Europe (13.4%) and North America (15.8%). Some representative countries, such as Japan, have a prevalence of 525/10,000 person-years, which is also much higher than that of the United States (130/10,000 person-years) and the United Kingdom (315/10,000 person-years) [\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e29\u003c/span\u003e]. Moreover, the cause of this phenomenon remains unknown. Here, we focus on the crural index as an influencing factor, which may be one of the reasons. The crural index in East Asia, represented by China and Japan, is usually less than 0.83 and is known as the short tibia type, whereas the crural index in the United States and Australia is usually greater than 0.83 and is known as the long tibia type [\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e30\u003c/span\u003e]. In addition, the crural index in females is usually lower than that in males [\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e31\u003c/span\u003e]. Therefore, we believe that the crural index, a less studied factor, may be a potential factor in the development of knee OA.\u003c/p\u003e \u003cp\u003eThis study had some limitations. First, because this was a single-center retrospective cross-sectional study, we were unable to thoroughly clarify the causal relationship between the crural index and knee OA. Additionally, the sample was relatively homogeneous and lacked generalizability, as most patients were female and Asian. Furthermore, the crural index differed among different races[\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e30\u003c/span\u003e]; therefore, caution should be exercised when applying the results of this study to other groups. However, given the multitude of factors influencing OA, it's improbable for one single factor to have an excessively high impact. The correlation coefficients we've obtained suggest that the crural index is indeed an important parameter, despite the complex interplay of contributing factors to OA.\u003c/p\u003e \u003cp\u003eIn conclusion, our findings indicate a close association between the crural index, knee OA, and knee alignment. Consequently, we propose that the crural index should be recognized as a risk factor for knee OA, warranting further consideration in preventive treatments and more comprehensive studies.\u003c/p\u003e"},{"header":"Abbreviations","content":"\u003cdiv id=\"AGS1\" class=\"AbbreviationGroupSection\"\u003e \u003cdiv class=\"Heading\"\u003e\u003c/div\u003e \u003cdiv class=\"DefinitionList\"\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003e\u003cb\u003eOA\u003c/b\u003e\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eOsteoarthritis\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003e\u003cb\u003eHKA\u003c/b\u003e\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eHip-knee-ankle angle\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003e\u003cb\u003eMAD\u003c/b\u003e\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eMechanical axis deflection\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003e\u003cb\u003emLDFA\u003c/b\u003e\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eMechanical lateral distal femoral angle\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003e\u003cb\u003eMPTA\u003c/b\u003e\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eMedial proximal tibial angle\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003e\u003cb\u003eaHKA\u003c/b\u003e\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eArithmetic hip-knee-ankle angle\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003e\u003cb\u003eFBL\u003c/b\u003e\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eFemur bicondylar length\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003e\u003cb\u003eTML\u003c/b\u003e\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eTibia maximum length\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003c/div\u003e \u003c/div\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eAvailability of data and materials\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eCan be requested from the corresponding author\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis study has received funding by Shanghai \u0026quot;Rising Stars of Medical Talent\u0026quot; Youth Development Program, Youth Medical Talents-Specialist Program, (SHHWRS 2023-62) and National Natural Science Foundation of China (Grant No. 31900941).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConflict of Interest:\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors of this manuscript declare no relationships with any companies, whose products or services may be related to the subject matter of the article.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eStatistics and Biometry:\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNo complex statistical methods were necessary for this paper.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eInformed Consent:\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eWritten informed consent was not required for this study because the biological information and data of the imaging data used in the study have been de-labelled, which meant they were not individually identifiable and traceable. Exemption from obtaining the informed consent of the subject would not have a negative impact on the rights and interests of the subject.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eEthical Approval:\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis observational cross-sectional study was approved by the Medical Ethics Committee (SH9H-2023-T257-1). The biological information and imaging data used in the study have been anonymised, which means they are not individually identifiable or traceable. Exemption from obtaining informed consent from the subjects will not have a negative impact on the rights or interests of the subjects.\u003c/p\u003e\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003eXiaofeng Shi: Conceptualization, Methodology, Data curation, Investigation, Writing \u0026ndash; original draft.Yibin Lu: Methodology, Investigation, Writing \u0026ndash; original draft.Hongyu Chen:Methodology, Formal analysis.Xinlin Jia: Data curation, literature review.YuanQing Mao: Project administration, Supervision.Jingwei Zhang: Writing \u0026ndash; review \u0026amp; editing, Supervision, Project administration, Funding acquisition.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eGlyn-Jones S, Palmer AJ, Agricola R, London et al. England), 386(9991), 376\u0026ndash;87.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eMartel-Pelletier J, Barr AJ, Cicuttini FM et al. (2016). Osteoarthritis. Nature reviews. Disease primers, 2, 16072.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eMahmoudian A, Lohmander LS, Mobasheri A, et al. Early-stage symptomatic osteoarthritis of the knee \u0026mdash; time for action. Nat Rev Rheumatol. 2021;17:621\u0026ndash;32.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eNeogi T, Bowes MA, Niu J, et al. Magnetic resonance imaging-based three-dimensional bone shape of the knee predicts onset of knee osteoarthritis: data from the osteoarthritis initiative. Arthritis Rheum. 2013;65(8):2048\u0026ndash;58.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eHashemi J, Chandrashekar N, Gill B, et al. The geometry of the tibial plateau and its influence on the biomechanics of the tibiofemoral joint. J Bone Joint Surg Am Vol. 2008;90(12):2724\u0026ndash;34.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSharma L, et al. Varus and valgus alignment and incident and progressive knee osteoarthritis. Ann Rheum Dis. 2010;69:1940\u0026ndash;5.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSharma L, Song J, Dunlop D, et al. Varus and valgus alignment and incident and progressive knee osteoarthritis. Ann Rheum Dis. 2010;69(11):1940\u0026ndash;5.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSharma L, Chmiel JS, Almagor O, et al. The role of varus and valgus alignment in the initial development of knee cartilage damage by MRI: the MOST study. Ann Rheum Dis. 2013;72(2):235\u0026ndash;40.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eDavenport CB. The crural index. Am J Phys Anthropol. 1933;17:333\u0026ndash;53.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003e\u003cem\u003eHolliday T. W. (\u003c/em\u003e1999). Brachial and crural indices of European late Upper Paleolithic and Mesolithic humans. J Hum Evol, 36(5), 549\u0026ndash;66.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eRoseman CC, Auerbach BM. \u003cem\u003e(\u003c/em\u003e2015). Ecogeography, genetics, and the evolution of human body form. Journal of human evolution, 78, 80\u0026ndash;90.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003ePhinney TL, Mussett EG, Duoos BA. Relationship of Crural Index and Speed in Collegiate Softball Players. Res Q Exerc Sport. 2015;86:A12\u0026ndash;3.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eGruss LT, Schmitt D. (2000). Effects of variation in crural index on the kinematics and kinetics of human walking. Am J Phys Anthropol, 167\u0026ndash;8.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eMarques Lu\u0026iacute;s, \u003cem\u003eN., \u0026amp;\u003c/em\u003e Varatojo, R. \u003cem\u003e(2021). Radiological assessment of lower limb alignment.\u003c/em\u003e EFORT open reviews, 6(6), 487\u0026ndash;494.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eGarcia, Reina V. (2015). The Brachial and Crural Indices of Modern North American Populations. May; pp. 19\u0026ndash;20.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLangley NR, Jantz LM, Ousley SD, Jantz RL, Milner G. (2016) Data collection procedures for forensic skeletal MATERIAL 2.0; p79\u0026ndash;80.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLei K, Liu L, Yang L, Guo L, Fu D. \u003cem\u003e(\u003c/em\u003e2023). A Torn Discoid Lateral Meniscus Impacts Lower-Limb Alignment Regardless of Age: Surgical Treatment May Not Be Appropriate for an Asymptomatic Discoid Lateral Meniscus. The Journal of bone and joint surgery. American volume, 105(13), 1020\u0026ndash;1025.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003ePlancher KD, Brite JE, Briggs KK, Petterson SC. \u003cem\u003e(\u003c/em\u003e2022). Pre-Arthritic/Kinematic Alignment in Fixed-Bearing Medial Unicompartmental Knee Arthroplasty Results in Return to Activity at Mean 10-Year Follow-up. The Journal of bone and joint surgery. American volume, 104(12), 1081\u0026ndash;1089.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eMacDessi, S. J., Griffiths-Jones, W., Harris, I. A., Bellemans, \u003cem\u003eJ., \u0026amp;\u003c/em\u003e Chen, D. B. \u003cem\u003e(\u003c/em\u003e2020). The arithmetic HKA (aHKA) predicts the constitutional alignment of the arthritic knee compared to the normal contralateral knee: a matched-pairs radiographic study. Bone \u0026amp; joint open, 1(7), 339\u0026ndash;345.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eKellgren JH, Lawrence JS. Radiological assessment of osteo-arthrosis. Ann Rheum Dis. 1957;16(4):494\u0026ndash;502.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eEngh GA. (2003). The difficult knee: severe varus and valgus. Clin Orthop Relat Res, (416), 58\u0026ndash;63.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLi M, Zeng Y, Nie Y, Wu Y, Liu Y, Wu L, Shen B. \u003cem\u003e(\u003c/em\u003e2022). Varus-valgus knee laxity is related to a higher risk of knee osteoarthritis incidence and structural progression: data from the osteoarthritis initiative. Clinical rheumatology, 41(4), 1013\u0026ndash;1021.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eNoyes FR, Schipplein OD, Andriacchi TP, Saddemi SR, Weise M. \u003cem\u003e(\u003c/em\u003e1992). The anterior cruciate ligament-deficient knee with varus alignment. An analysis of gait adaptations and dynamic joint loadings. The American journal of sports medicine, 20(6), 707\u0026ndash;716.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eMacDessi SJ, Griffiths-Jones W, Harris IA, Bellemans J, Chen DB. \u003cem\u003e(\u003c/em\u003e2021). Coronal Plane Alignment of the Knee (CPAK) classification. The bone \u0026amp; joint journal, 103-B(2), 329\u0026ndash;337.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eKun E, Javan EM, Smith O, et al. The genetic architecture and evolution of the human skeletal form. Volume 381. Science (New York; 2023. p. eadf8009. 6655.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eKhalaj N, Abu Osman NA, Mokhtar AH, Mehdikhani M, Wan Abas WA. \u003cem\u003e(\u003c/em\u003e2014). Effect of exercise and gait retraining on knee adduction moment in people with knee osteoarthritis. Proceedings of the Institution of Mechanical Engineers. Part H, Journal of engineering in medicine, 228(2), 190\u0026ndash;199.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eShaw KE, Charlton JM, Perry CK, et al. The effects of shoe-worn insoles on gait biomechanics in people with knee osteoarthritis: a systematic review and meta-analysis. Br J Sports Med. 2018;52(4):238\u0026ndash;53. L.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSafiri S, Kolahi AA, Smith E, et al. Global, regional and national burden of osteoarthritis 1990\u0026ndash;2017: a systematic analysis of the Global Burden of Disease Study 2017. Ann Rheum Dis. 2020;79(6):819\u0026ndash;28.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eCui A, Li H, Wang D, Zhong J, Chen Y, Lu H. \u003cem\u003e(\u003c/em\u003e2020). Global, regional prevalence, incidence and risk factors of knee osteoarthritis in population-based studies. EClinicalMedicine, 29\u0026ndash;30, 100587.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eAuerbach BM, Ruff CB. Stature estimation formulae for indigenous North American populations. Am J Phys Anthropol. 2010;141(2):190\u0026ndash;207.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eNuger RL. (2009). Sex differences in brachial and crural indices in relation to climate. Am J Phys Anthropol, 200\u0026ndash;1.\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","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":"knee osteoarthritis, the crural index, knee alignment","lastPublishedDoi":"10.21203/rs.3.rs-4166157/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-4166157/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003ch2\u003eBackground\u003c/h2\u003e \u003cp\u003eThe crural index, a fundamental property of the human skeletal system, is the ratio of the total length of the tibia to that of the femur. This study aimed to investigate the correlation between the crural index and knee osteoarthritis (OA).\u003c/p\u003e\u003ch2\u003eMethods\u003c/h2\u003e \u003cp\u003eThis observational cross-sectional study included patients with preoperative weight-bearing full-length radiographs who were divided into two groups according to the Kellgren\u0026ndash;Lawrence grading system. After rigorous screening based on the inclusion and exclusion criteria, 92 and 125 patients were included in the control and knee OA groups, respectively. The crural index, hip-knee-ankle angle (HKA), the deviation of the HKA from 180\u0026deg; (|HKA-180|), mechanical axis deflection (MAD), mechanical lateral distal femoral angle (mLDFA), medial proximal tibial angle (MPTA), arithmetic HKA (aHKA), and |aHKA| were compared between the two groups. In addition, linear regressions of the crural index were performed to assess their correlations.\u003c/p\u003e\u003ch2\u003eResults\u003c/h2\u003e \u003cp\u003eThe crural index was significantly smaller in the knee OA group than in the control group (crural index: 79.49\u0026thinsp;\u0026plusmn;\u0026thinsp;2.39 versus 82.14\u0026thinsp;\u0026plusmn;\u0026thinsp;2.22, respectively; p\u0026thinsp;\u0026lt;\u0026thinsp;0.001). The crural index correlated well with both |HKA-180| (R\u0026sup2; = 0.54, p\u0026thinsp;\u0026lt;\u0026thinsp;0.05) and MAD (R\u0026sup2; = 0.57, p\u0026thinsp;\u0026lt;\u0026thinsp;0.05).\u003c/p\u003e\u003ch2\u003eConclusions\u003c/h2\u003e \u003cp\u003ePatients with OA of the knee have a much smaller crural index, which was closely related to the knee alignment.\u003c/p\u003e","manuscriptTitle":"Does having shorter tibias increase the likelihood of developing knee osteoarthritis? An observational cross-sectional radiographic analysis","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2024-04-02 19:01:39","doi":"10.21203/rs.3.rs-4166157/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":"0786649e-e735-458e-8d29-433b528ac106","owner":[],"postedDate":"April 2nd, 2024","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2024-04-16T14:37:02+00:00","versionOfRecord":[],"versionCreatedAt":"2024-04-02 19:01:39","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-4166157","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-4166157","identity":"rs-4166157","version":["v1"]},"buildId":"qtupq5eGEP_6zYnWcrvyt","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}