Knee pain in young sports players aged 6 to 15 years: a cross-sectional study in Japan

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Nevertheless, few studies with large sample size have been published reporting the difference of the prevalence of knee pain for each sport among young sports players. Methods This study was to investigate the point prevalence of knee pain according to age, sex and sports discipline and the association between knee pain and sports discipline among young sports players. A cross-sectional study was conducted using a self-reported questionnaire on young sports players aged 6–15 years who belonged to the Miyagi Amateur Sports Association. Multivariable logistic regression models were used to examine the association between knee pain and sports discipline and were adjusted for age, sex, training days per week, and training hours per weekday and weekend. Results A total of 7234 young sports players were included. The point prevalence of knee pain was 10.9%. Females (13.3%) had more knee pain than males (9.8%). 13 years had the highest prevalence of knee pain (19.1%). In multivariable analysis, mini-basketball (odds ratio, 1.90; 95% CI, 1.44–2.52) and basketball (odds ratio, 1.62; 95% CI, 1.20–2.18) were significantly associated with knee pain, compared with football. Conclusion The prevalence of knee pain among young athletes differed according to age, sex, and sports discipline. Their parents and clinicians should recognize this information to manage knee pain prevention among young sports players. knee pain young sports players sports discipline Figures Figure 1 Figure 2 Introduction Knee pain is a major symptom among those involved in sports, with 37% of all sport injuries being related to the knee joint [ 1 ]. In children and adolescents, lower-extremity complaints occur more often than upper-extremity complaints, and knee complaints are most frequent in children aged 10–19 years [ 2 ]. Vähäsarja et al. reported that 18.5% of children aged 14–15 years had chronic knee pain [ 3 ]. Several researchers have described that the knee is the most commonly injured part of the body in young athletes, with the prevalence of knee pain ranging from 5–26%, depending on sport types [ 4 ]. Acute and chronic injuries such as osteoarthritis, jumper’s knee, Osgood-Schlatter disease, patellofemoral pain syndrome, and infection are the major causes of knee pain in adolescents and adults [ 5 ]. Among young athletes, a common cause of knee pain is overuse injury, including Osgood-Schlatter disease and Sinding-Larsen-Johansson syndrome [ 6 ]. Most young athletes with knee injuries are able to return to sports activity through conservative treatment [ 7 ]. However, knee pain related to sports activities is commonly recurrent or chronic [ 8 ], and overuse injury can have long-term consequences in young athletes [ 9 ]. Rathleff et al. reported that adolescents with knee pain had lower EuroQoL-5 dimension scores than adolescents without knee pain, suggesting that knee pain affects their daily life and health [ 10 ]. Some researchers have reported risk factors for knee pain among young athletes in several sports disciplines [ 3 , 11 – 15 ]. Associated clinical factors for knee pain include female sex [ 13 ], older age [ 3 , 11 , 14 ], more frequent sports participation [ 12 , 15 ], and type of sport [ 12 ]. Nonetheless, these studies have limited sample sizes. Junge et al. reported risk factors for knee injuries among 1326 young athletes aged 8–15 years in nine sports [ 12 ]. Majewski et al. reported on the epidemiology of knee injuries in 6434 athletes across all age groups, including children and adolescents, among 26 types of sports [ 1 ]. However, only a small number of studies comparing knee pain among different sports disciplines in young athletes had been conducted. Therefore, the present study aimed to report on the point prevalence of knee pain in young athletes aged 6–15 years among 14 different types of sports and to investigate the association between knee pain and sports discipline. Materials And Methods Participants A cross-sectional study was conducted on 25469 young sports players aged 6–15 years who belonged to the Miyagi Amateur Sports Association located in Miyagi Prefecture, Japan [16]. A self-reported questionnaire was sent to all young sports players in October 2014. The participants completed the questionnaires themselves or with the help of their parents, when necessary, particularly in the case of younger participants [17]. A total of 7333 athletes (28.8%) who consented to the study completed the questionnaire by the end of December 2014. Participants with missing age or sex data (n=56) and those who played several sports (n=43) were excluded from the analysis. Finally, 7234 young sports players were enrolled in this study (Figure 1). This study was conducted in accordance with the principles embodied in the Declaration of Helsinki, and the study protocol was approved by the institutional review board of Tohoku University School of Medicine (approval number: 2013-564). Questionnaires The questionnaires were used to obtain data on participants’ age, sex, type of sport played, number of training days per week, and number of training hours per weekday and weekend. In addition, knee pain was assessed by a self-reported questionnaire. Participants were considered to have knee pain if they answered “yes” to the question which was “Do you have any pain in any parts of your body?” and specified the knee as the location of their pain by checking knee area which was illustrated by drawing [18]. Statistical Analysis Continuous variables are presented as means and standard deviations, whereas categorical variables are expressed as numbers and percentages. The prevalence of knee pain was calculated based on age, sex, and sports discipline (the number of participants more than 30). Multivariable logistic regression models were used to examine the association between knee pain and sports discipline and were adjusted for age, sex, training days per week, and training hours per weekday and weekend. The results are presented as odds ratios (ORs) with 95% confidence intervals (CIs). This study had no control group; therefore, football, which is often reported as a sport that commonly causes knee pain [11, 14], was used as the reference sport in the multivariable analysis. All statistical analyses were performed using SPSS 24.0 (SPSS Japan Inc., Tokyo, Japan), with a P value of <0.05 being considered to be indicative of statistical significance. Results Baseline Characteristics The baseline characteristics of participants are presented in Table 1. Among 7234 participants, the mean age was 10.8 years (range, 6–15 years) and the number of males and females was 5082 (70.3%) and 2152 (29.7%), respectively. Fourteen types of sports were included in this study, with baseball being the most popular sport (1748 participants), followed by football (1477 participants) (Table 1). Prevalence of Knee Pain According to Age and Sex The overall point prevalence of knee pain was 10.9% (n=787). The prevalence of knee pain was 9.8% (n=500) among males and 13.3% (n=287) among females. Participants aged 6 reported no knee pain. The prevalence of knee pain tended to increase with age. Approximately 19.1% of participants aged 13 years reported knee pain. In 9- and more than 9-year-old participants, the prevalence of knee pain was higher in females than in males (Figure 2A). Prevalence of Knee Pain According to Sports Discipline The prevalence of knee pain according to sports and sex is shown in Figure 2B. Among the 14 sports, basketball players had the highest prevalence of knee pain (25.1%), followed by handball (19.5%), mini-basketball (16.4%), and badminton (13.0%) players. In males, the highest prevalence of knee pain was observed among basketball players (24.5%) followed by handball (16.7%), mini-basketball (15.9%) and volleyball (14.4%) participants. In females, the highest prevalence of knee pain was observed among basketball participants (25.9%), followed by handball (23.5%), mini-basketball (17.1%) and swimming (16.7%) participants. The lowest prevalence of knee pain was observed among karate participants (3.8%), followed by swimming (4.9%), baseball (6.3%), and kendo (6.9%) participants. The prevalence of knee pain was higher among females than among males in all sports, except for volleyball, judo, football and baseball. Association Between Sports Discipline and Knee Pain After adjustment for sex, age, training days per week, and training hours per weekday and weekend, the highest adjusted OR was observed for handball (OR 2.27; 95% CI 0.95–5.42), followed by mini-basketball (OR 1.90; 95% CI 1.44–2.52) and basketball (OR 1.62; 95% CI 1.20–2.18). With football as the reference sport, mini-basketball and basketball were identified to be significantly associated with knee pain. Furthermore, the lowest adjusted OR was observed for swimming (OR 0.32; 95% CI 0.04–2.35), followed by karate (OR 0.44; 95% CI 0.20–0.96) and baseball (OR 0.48; 95%CI 0.36–0.65) (Table 2). Discussion We examined knee pain in 7234 young sports players aged 6–15 years who participated in 14 different sports. The most important finding of this study was that the prevalence of knee pain was different according to age, sex, and type of sport. The prevalence of knee pain increased with age, and 13-year-old athletes had the highest rate of knee pain. In 9 and more than 9 years, females had more knee pain than males. Among the different sports disciplines, mini-basketball and basketball were significantly associated with higher rates of knee pain compared with football in the multivariable analysis. There have been few reports showing the prevalence of knee pain among young sports players with large sample size [11, 19, 20]. Hall et al. reported the point prevalence of patellofemoral pain among 546 female basketball, soccer and volleyball players in middle schools and high schools was 28% [19]. Iwame et al. reported the point prevalence of knee pain was 29.4% among 602 boy soccer players aged 8 to 12 years.[11] Rathleff et al. described that the point prevalence of knee pain was 23% among 2200 adolescents aged 15–19 years [20]. In this study, the point prevalence of knee pain among 7234 young athletes aged 6–15 years was 10.9% (n=787), which was lower than that reported by previous studies. The difference in age distribution, intensity of sports activity, and methodology of the study might have influenced these results. Furthermore, none of the participants aged 6 years had knee pain, which can be one of the main reasons for the lower rate of knee pain in our study population. Some researchers have reported that the prevalence of knee pain increases with age [3, 11, 14]. Vähäsarja et al. reported that the prevalence of knee pain was significantly higher in adolescents aged 14–15 years than in those aged 9–10 years [3]. Furthermore, Iwame et al. reported that young athletes aged 9 or older had significantly higher rates of knee pain than those aged less than 9 years [11]. In this study, the proportion of knee pain increased with age, and 13–year-old participants had the highest rate of knee pain. The amount of training increased with older age [21], which was reported to be a risk factor for the development of jumper’s knee [15]. Increasing the amount of training might cause knee pain with older age. Furthermore, Wild et al. showed that the growth spurt during adolescence caused musculoskeletal changes, which increased anterior cruciate ligament injuries [22]. The highest rate of knee pain observed among athletes aged 13 years in this study might be associated with this growth spurt. Many researchers have reported a higher proportion of knee pain in females than male [13, 23, 24]. Similar findings were observed in our study among all players. Differences in hip muscle strength [25] and knee joint alignment [26, 27] between males and females are known to influence the incidence of knee pain. Ford et al. reported that the knee abduction angle was greater in young female athletes than in males, which was associated with higher rates of anterior cruciate ligament injury in females [26]. In contrast, Yang et al. reported that among high school athletes, males had a higher proportion of knee injuries than females [28]. In this study, with respect to sports discipline, males had a higher prevalence of knee pain than females who played volleyball, judo, football and baseball. These results indicate that knee pain can vary according to sex and sports discipline. The association between sports discipline and knee pain has also been reported in previous studies with small number of types of sports [11, 12]. Lian et al. reported that the prevalence of jumper’s knee was the highest among elite athletes of volleyball and basketball in a study of 9 sports disciplines [29]. Junge et al. reported that participation in football, handball, basketball, and rhythmic and tumbling gymnastics were risk factors for overuse knee injuries in children aged 8–15 years in 9 types of sport [12]. The prevalence of knee pain was different among 14 different sports and the adjusted OR was the highest for handball, followed by mini-basketball, and basketball in this study. Mini-basketball and basketball were significantly associated with knee pain compared to football. Basketball and handball players repeatedly jump and shoot with arm swing and changes in their movement in all directions [30-32]. The specific movements and different mechanisms underlying knee injury for each sport may result in different knee pain prevalence rates [33], which should be clarified in future studies. The present study had some limitations. Firstly, the response rate was not high, and only 28.8% of athletes responded to the questionnaire. Secondly, the characteristics of knee pain, such as pain intensity, duration, location, and time of onset, were not assessed. Finally, participants were not longitudinally followed, and knee pain that was not confirmed to have occurred as a result of sport might have been due to other causes such as acute trauma or was unrelated to sport. Conclusions Based on this study, the prevalence of knee pain among young sports players differed according to age, sex, and sports discipline. Their parents and clinicians should recognize this information to prevent knee pain among young sports players by different exercises and programs based on the sports players’ age, sex and sports discipline. Declarations Ethical Approval and consent to participate The study protocol was reviewed and approved by the Ethics Committee on Research of Human Subjects at Tohoku University Graduate School of Medicine (Approved Number: 2013-564) All methods were carried out in accordance with relevant guidelines and regulations. Participants provided written informed consent before participating in the study. Parental/guardian informed consent forms were obtained for the participants who were younger than 16 years. Consent for publication Not applicable. Availability of data and materials The datasets used and/or analyzed during the current study are not publicly available due to including personal information but are available from the corresponding author on reasonable request. Competing interests The authors declare that they have no competing interests. Funding This study was funded by Asahi Soft Drink Co., Ltd. Author’s contribution JI wrote the manuscript. JI, TS, HM, MT, KK, SY and YS were involved in study design and data interpretation. YY, RN and YH helped to draft the manuscript. All authors read and approved the final manuscript. Acknowledgements This study was performed as part of the Miyagi Sports Medical Projects. It was supported by Asahi Soft Drink Co., Ltd. References Majewski M, Susanne H, Klaus S. Epidemiology of athletic knee injuries: A 10-year study. The Knee. 2006;13(3):184–8. Fuglkjær S, Dissing KB, Hestbæk L. Prevalence and incidence of musculoskeletal extremity complaints in children and adolescents. A systematic review. BMC Musculoskelet Disord. 2017;18(1):418. Vähäsarja V. Prevalence of chronic knee pain in children and adolescents in northern Finland. Acta Paediatr. 1995;84(7):803–5. Caine D, Caine C, Maffulli N. Incidence and distribution of pediatric sport-related injuries. Clin J Sport Med. 2006;16(6):500–13. Bunt CW, Jonas CE, Chang JG. Knee Pain in Adults and Adolescents: The Initial Evaluation. 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Baseline characteristics of participants Sports Discipline n Age, mean (SD) Male, n (%) Female, n (%) Practice days per week, mean (SD) Practice hours per day (weekdays), mean (SD) Practice hours per day (weekends), mean (SD) All players 7234 10.8 (1.9) 5082 (70.3) 2152 (29.7) 3.3 (1.5) 1.9 (1.1) 3.7 (2.1) Baseball 1748 10.8 (1.8) 1660 (95.0) 88 (5.0) 3.3 (1.5) 1.5 (1.3) 5.4 (2.2) Football 1477 10.3 (1.6) 1385 (93.8) 92 (6.2) 3.1 (1.1) 1.7 (0.9) 3.0 (1.2) Mini-basketball 797 10.3 (1.5) 434 (54.5) 363 (45.5) 3.7 (0.9) 2.3 (0.9) 3.4 (1.5) Volleyball 681 10.8 (1.8) 167 (24.5) 514 (75.5) 3.4 (1.3) 2.3 (1.4) 4.0 (2.3) Basketball 680 12.5 (1.6) 371 (54.6) 309 (45.4) 4.8 (1.7) 2.2 (0.7) 3.6 (1.6) Kendo 525 11.0 (2.2) 329 (62.7) 196 (37.3) 3.1 (1.2) 2.0 (0.9) 1.8 (1.2) Judo 242 11.0 (2.3) 178 (73.6) 64 (26.4) 2.9 (0.9) 2.1 (0.6) 1.6 (1.1) Karate 236 9.9 (2.2) 169 (71.6) 67 (28.4) 2.4 (1.1) 1.9 (0.8) 1.8 (1.5) Track and field 137 10.3 (1.7) 57 (41.6) 80 (58.4) 1.7 (0.9) 0.9 (0.9) 2.1 (0.6) Soft tennis 128 12.1 (1.9) 48 (37.5) 80 (62.5) 3.7 (1.9) 2.0 (0.8) 4.4 (2.5) Badminton 123 11. 3 (1.9) 39 (31.7) 84 (68.3) 2.9 (1.1) 2.1 (0.7) 3.5 (1.7) Table tennis 94 12.8 (1.9) 37 (39.4) 57 (60.6) 3.7 (1.9) 2.3 (0.8) 2.9 (1.8) Handball 41 11.2 (2.3) 24 (58.5) 17 (41.5) 3.3 (2.0) 2.7 (0.4) 3.3 (0.8) Swimming 41 9.9 (2.0) 29 (70.7) 12 (29.3) 2.4 (1.4) 1.2 (0.5) 1.0 (1.0) Others 284 11 (2.3) 155 (54.6) 129 (45.4) 2.4 (1.6) 1.7 (0.8) 2.7 (2.0) SD, standard deviation. Table 2. Association between sports discipline and knee pain in multivariate analysis Variables Adjusted OR (95% CI) Football 1.00 Handball 2.27 (0.95–5.42) Mini-basketball 1.90 (1.44–2.52) Basketball 1.62 (1.20–2.18) Badminton 1.21 (0.67–2.17) Volleyball 1.06 (0.75–1.49) Track and field 0.97 (0.47–2.01) Judo 0.94 (0.56–1.58) Table tennis 0.73 (0.37–1.46) Soft tennis 0.70 (0.37–1.31) Kendo 0.62 (0.41–0.95) Baseball 0.48 (0.36–0.65) Karate 0.44 (0.20–0.96) Swimming 0.32 (0.04–2.35) Others 1.21 (0.74–1.96) Adjusted for sex, age, training days per week, and training hours per weekday and per weekend. OR, odds ratio; CI, confidence interval. Additional Declarations No competing interests reported. Cite Share Download PDF Status: Published Journal Publication published 07 Feb, 2023 Read the published version in BMC Sports Science, Medicine and Rehabilitation → Version 1 posted Editorial decision: Major revision 24 Jun, 2022 Reviews received at journal 18 Jun, 2022 Reviewers agreed at journal 06 Jun, 2022 Reviewers invited by journal 04 Jun, 2022 Editor assigned by journal 04 Jun, 2022 Editor invited by journal 04 Jun, 2022 Submission checks completed at journal 04 Jun, 2022 First submitted to journal 27 May, 2022 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-1699129","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":111091957,"identity":"84617f10-0710-4a1e-b2a7-b9714106d010","order_by":0,"name":"Jun Iwatsu","email":"","orcid":"","institution":"Tohoku University School of Medicine","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Jun","middleName":"","lastName":"Iwatsu","suffix":""},{"id":111091960,"identity":"e82c7f70-4fef-4119-bbc8-0fd1daa776ef","order_by":1,"name":"Yutaka Yabe","email":"","orcid":"","institution":"Tohoku University School of 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Hagiwara","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA7ElEQVRIiWNgGAWjYBACAyA+8IGBgbGBgYENyESI4tVycAZICxspWph50LXgBebsxy8ets2xkW2Qbz724MOZwwz87QcYigvwaLHsySk4nLstzbiBjS3dcMaNwwwSZxIYjGfgc9iBnASglsOJDWw8ZtI8Hw4zMNxgYDDmwafl/JuEw5bb/iO0yBPUciP9wGHGbQegWoAOMyCs5Q3Dwd5tycZtbGlpkjPOpPMYnklswO+X8+mPP/zcZifbz3z4mMSHY9ZycscPHzPGF2IMDDyQeGODcYFx1GaMVwcD+wMMIebH+LWMglEwCkbBCAMAW5RQxJvbKG4AAAAASUVORK5CYII=","orcid":"","institution":"Tohoku University School of Medicine","correspondingAuthor":true,"submittingAuthor":false,"prefix":"","firstName":"Yoshihiro","middleName":"","lastName":"Hagiwara","suffix":""}],"badges":[],"createdAt":"2022-05-27 08:59:15","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-1699129/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-1699129/v1","draftVersion":[],"editorialEvents":[{"content":"https://doi.org/10.1186/s13102-022-00606-y","type":"published","date":"2023-02-07T18:46:26+00:00"}],"editorialNote":"","failedWorkflow":false,"files":[{"id":22303661,"identity":"e6aef096-8300-42be-b480-38d8f3ffe15a","added_by":"auto","created_at":"2022-06-06 14:47:01","extension":"jpg","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":155627,"visible":true,"origin":"","legend":"\u003cp\u003eStudy flow chart.\u003c/p\u003e","description":"","filename":"Figure1.jpg","url":"https://assets-eu.researchsquare.com/files/rs-1699129/v1/fe72074c18160566a442e028.jpg"},{"id":22303658,"identity":"5f0e27ae-07ba-4620-b56b-bb5281ae4828","added_by":"auto","created_at":"2022-06-06 14:47:01","extension":"jpg","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":275480,"visible":true,"origin":"","legend":"\u003cp\u003eA) The prevalence of knee pain categorized by age and sex, B) The Prevalence of knee pain categorized by sports discipline and sex\u003c/p\u003e","description":"","filename":"Figure2.jpg","url":"https://assets-eu.researchsquare.com/files/rs-1699129/v1/81f52ef490d7d744f92e3700.jpg"},{"id":44719232,"identity":"cdce6b9a-baae-43e6-a636-f1d9d4bcce3c","added_by":"auto","created_at":"2023-10-16 18:53:59","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":556278,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-1699129/v1/709454fe-e7e9-4fb8-8ef7-4b712361ef83.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Knee pain in young sports players aged 6 to 15 years: a cross-sectional study in Japan","fulltext":[{"header":"Introduction","content":"\u003cp\u003eKnee pain is a major symptom among those involved in sports, with 37% of all sport injuries being related to the knee joint [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e]. In children and adolescents, lower-extremity complaints occur more often than upper-extremity complaints, and knee complaints are most frequent in children aged 10\u0026ndash;19 years [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]. V\u0026auml;h\u0026auml;sarja et al. reported that 18.5% of children aged 14\u0026ndash;15 years had chronic knee pain [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e]. Several researchers have described that the knee is the most commonly injured part of the body in young athletes, with the prevalence of knee pain ranging from 5\u0026ndash;26%, depending on sport types [\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e]. Acute and chronic injuries such as osteoarthritis, jumper\u0026rsquo;s knee, Osgood-Schlatter disease, patellofemoral pain syndrome, and infection are the major causes of knee pain in adolescents and adults [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e]. Among young athletes, a common cause of knee pain is overuse injury, including Osgood-Schlatter disease and Sinding-Larsen-Johansson syndrome [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e]. Most young athletes with knee injuries are able to return to sports activity through conservative treatment [\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e]. However, knee pain related to sports activities is commonly recurrent or chronic [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e], and overuse injury can have long-term consequences in young athletes [\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e]. Rathleff et al. reported that adolescents with knee pain had lower EuroQoL-5 dimension scores than adolescents without knee pain, suggesting that knee pain affects their daily life and health [\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eSome researchers have reported risk factors for knee pain among young athletes in several sports disciplines [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e, \u003cspan additionalcitationids=\"CR12 CR13 CR14\" citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e]. Associated clinical factors for knee pain include female sex [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e], older age [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e, \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e, \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e], more frequent sports participation [\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e, \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e], and type of sport [\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e]. Nonetheless, these studies have limited sample sizes. Junge et al. reported risk factors for knee injuries among 1326 young athletes aged 8\u0026ndash;15 years in nine sports [\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e]. Majewski et al. reported on the epidemiology of knee injuries in 6434 athletes across all age groups, including children and adolescents, among 26 types of sports [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e]. However, only a small number of studies comparing knee pain among different sports disciplines in young athletes had been conducted. Therefore, the present study aimed to report on the point prevalence of knee pain in young athletes aged 6\u0026ndash;15 years among 14 different types of sports and to investigate the association between knee pain and sports discipline.\u003c/p\u003e"},{"header":"Materials And Methods","content":"\u003cp\u003e\u003cstrong\u003eParticipants\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eA cross-sectional study was conducted on 25469 young sports players aged 6\u0026ndash;15 years who belonged to the Miyagi Amateur Sports Association located in Miyagi Prefecture, Japan [16]. A self-reported questionnaire was sent to all young sports players in October 2014. The participants completed the questionnaires themselves or with the help of their parents, when necessary, particularly in the case of younger participants [17]. A total of 7333 athletes (28.8%) who consented to the study completed the questionnaire by the end of December 2014. Participants with missing age or sex data (n=56) and those who played several sports (n=43) were excluded from the analysis. Finally, 7234 young sports players were enrolled in this study (Figure 1). This study was conducted in accordance with the principles embodied in the Declaration of Helsinki, and the study protocol was approved by the institutional review board of Tohoku University School of Medicine (approval number: 2013-564).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eQuestionnaires\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe questionnaires were used to obtain data on participants\u0026rsquo; age, sex, type of sport played, number of training days per week, and number of training hours per weekday and weekend. In addition, knee pain was assessed by a self-reported questionnaire. Participants were considered to have knee pain if they answered \u0026ldquo;yes\u0026rdquo; to the question which was \u0026ldquo;Do you have any pain in any parts of your body?\u0026rdquo; and specified the knee as the location of their pain by checking knee area which was illustrated by drawing [18].\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eStatistical Analysis\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eContinuous variables are presented as means and standard deviations, whereas categorical variables are expressed as numbers and percentages. The prevalence of knee pain was calculated based on age, sex, and sports discipline (the number of participants more than 30). Multivariable logistic regression models were used to examine the association between knee pain and sports discipline and were adjusted for age, sex, training days per week, and training hours per weekday and weekend. The results are presented as odds ratios (ORs) with 95% confidence intervals (CIs). This study had no control group; therefore, football, which is often reported as a sport that commonly causes knee pain [11, 14], was used as the reference sport in the multivariable analysis. All statistical analyses were performed using SPSS 24.0 (SPSS Japan Inc., Tokyo, Japan), with a P value of \u0026lt;0.05 being considered to be indicative of statistical significance.\u003c/p\u003e"},{"header":"Results","content":"\u003cp\u003e\u003cstrong\u003eBaseline Characteristics\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe baseline characteristics of participants are presented in Table 1. Among 7234 participants, the mean age was 10.8 years (range, 6\u0026ndash;15 years) and the number of males and females was 5082 (70.3%) and 2152 (29.7%), respectively. Fourteen types of sports were included in this study, with baseball being the most popular sport (1748 participants), followed by football (1477 participants) (Table 1).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003ePrevalence of Knee Pain According to Age and Sex\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe overall point prevalence of knee pain was 10.9% (n=787). The prevalence of knee pain was 9.8% (n=500) among males and 13.3% (n=287) among females. Participants aged 6 reported no knee pain. The prevalence of knee pain tended to increase with age. Approximately 19.1% of participants aged 13 years reported knee pain. In 9- and more than 9-year-old participants, the prevalence of knee pain was higher in females than in males (Figure 2A).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003ePrevalence of Knee Pain According to Sports Discipline\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe prevalence of knee pain according to sports and sex is shown in Figure 2B. Among the 14 sports, basketball players had the highest prevalence of knee pain (25.1%), followed by handball (19.5%), mini-basketball (16.4%), and badminton (13.0%) players. In males, the highest prevalence of knee pain was observed among basketball players (24.5%) followed by handball (16.7%), mini-basketball (15.9%) and volleyball (14.4%) participants. In females, the highest prevalence of knee pain was observed among basketball participants (25.9%), followed by handball (23.5%), mini-basketball (17.1%) and swimming (16.7%) participants. The lowest prevalence of knee pain was observed among karate participants (3.8%), followed by swimming (4.9%), baseball (6.3%), and kendo (6.9%) participants. The prevalence of knee pain was higher among females than among males in all sports, except for volleyball, judo, football and baseball.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAssociation Between Sports Discipline and Knee Pain\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eAfter adjustment for sex, age, training days per week, and training hours per weekday and weekend, the highest adjusted OR was observed for handball (OR 2.27; 95% CI 0.95\u0026ndash;5.42), followed by mini-basketball (OR 1.90; 95% CI 1.44\u0026ndash;2.52) and basketball (OR 1.62; 95% CI 1.20\u0026ndash;2.18). With football as the reference sport, mini-basketball and basketball were identified to be significantly associated with knee pain. Furthermore, the lowest adjusted OR was observed for swimming (OR 0.32; 95% CI 0.04\u0026ndash;2.35), followed by karate (OR 0.44; 95% CI 0.20\u0026ndash;0.96) and baseball (OR 0.48; 95%CI 0.36\u0026ndash;0.65) (Table 2).\u003c/p\u003e"},{"header":"Discussion","content":"\u003cp\u003eWe examined knee pain in 7234 young sports players aged 6\u0026ndash;15 years who participated in 14 different sports. The most important finding of this study was that the prevalence of knee pain was different according to age, sex, and type of sport. The prevalence of knee pain increased with age, and 13-year-old athletes had the highest rate of knee pain. In 9 and more than 9 years, females had more knee pain than males. Among the different sports disciplines, mini-basketball and basketball were significantly associated with higher rates of knee pain compared with football in the multivariable analysis.\u003c/p\u003e\n\u003cp\u003eThere have been few reports showing the prevalence of knee pain among young sports players with large sample size [11, 19, 20]. Hall et al. reported the point prevalence of patellofemoral pain among 546 female basketball, soccer and volleyball players in middle schools and high schools was 28% [19]. Iwame et al. reported the point prevalence of knee pain was 29.4% among 602 boy soccer players aged 8 to 12 years.[11] Rathleff et al. described that the point prevalence of knee pain was 23% among 2200 adolescents aged 15\u0026ndash;19 years [20]. In this study, the point prevalence of knee pain among 7234 young athletes aged 6\u0026ndash;15 years was 10.9% (n=787), which was lower than that reported by previous studies. The difference in age distribution, intensity of sports activity, and methodology of the study might have influenced these results. Furthermore, none of the participants aged 6 years had knee pain, which can be one of the main reasons for the lower rate of knee pain in our study population.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eSome researchers have reported that the prevalence of knee pain increases with age [3, 11, 14]. V\u0026auml;h\u0026auml;sarja et al. reported that the prevalence of knee pain was significantly higher in adolescents aged 14\u0026ndash;15 years than in those aged 9\u0026ndash;10 years [3]. Furthermore, Iwame et al. reported that young athletes aged 9 or older had significantly higher rates of knee pain than those aged less than 9 years [11]. In this study, the proportion of knee pain increased with age, and 13\u0026ndash;year-old participants had the highest rate of knee pain. The amount of training increased with older age [21], which was reported to be a risk factor for the development of jumper\u0026rsquo;s knee [15]. Increasing the amount of training might cause knee pain with older age. Furthermore, Wild et al. showed that the growth spurt during adolescence caused musculoskeletal changes, which increased anterior cruciate ligament injuries [22]. The highest rate of knee pain observed among athletes aged 13 years in this study might be associated with this growth spurt.\u003c/p\u003e\n\u003cp\u003eMany researchers have reported a higher proportion of knee pain in females than male [13, 23, 24]. Similar findings were observed in our study among all players. Differences in hip muscle strength [25] and knee joint alignment [26, 27] between males and females are known to influence the incidence of knee pain. Ford et al. reported that the knee abduction angle was greater in young female athletes than in males, which was associated with higher rates of anterior cruciate ligament injury in females [26]. In contrast, Yang et al. reported that among high school athletes, males had a higher proportion of knee injuries than females [28]. In this study, with respect to sports discipline, males had a higher prevalence of knee pain than females who played volleyball, judo, football and baseball. These results indicate that knee pain can vary according to sex and sports discipline.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eThe association between sports discipline and knee pain has also been reported in previous studies with small number of types of sports [11, 12]. Lian et al. reported that the prevalence of jumper\u0026rsquo;s knee was the highest among elite athletes of volleyball and basketball in a study of 9 sports disciplines [29]. Junge et al. reported that participation in football, handball, basketball, and rhythmic and tumbling gymnastics were risk factors for overuse knee injuries in children aged 8\u0026ndash;15 years in 9 types of sport [12]. The prevalence of knee pain was different among 14 different sports and the adjusted OR was the highest for handball, followed by mini-basketball, and basketball in this study. Mini-basketball and basketball were significantly associated with knee pain compared to football. Basketball and handball players repeatedly jump and shoot with arm swing and changes in their movement in all directions [30-32]. The specific movements and different mechanisms underlying knee injury for each sport may result in different knee pain prevalence rates [33], which should be clarified in future studies.\u003c/p\u003e\n\u003cp\u003eThe present study had some limitations. Firstly, the response rate was not high, and only 28.8% of athletes responded to the questionnaire. Secondly, the characteristics of knee pain, such as pain intensity, duration, location, and time of onset, were not assessed. Finally, participants were not longitudinally followed, and knee pain that was not confirmed to have occurred as a result of sport might have been due to other causes such as acute trauma or was unrelated to sport.\u003c/p\u003e"},{"header":"Conclusions","content":"\u003cp\u003eBased on this study, the prevalence of knee pain among young sports players differed according to age, sex, and sports discipline. Their parents and clinicians should recognize this information to prevent knee pain among young sports players by different exercises and programs based on the sports players\u0026rsquo; age, sex and sports discipline.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eEthical Approval and consent to participate\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe study protocol was reviewed and approved by the Ethics Committee on Research of Human Subjects at Tohoku University Graduate School of Medicine (Approved Number: 2013-564) All methods were carried out in accordance with relevant guidelines and regulations.\u0026nbsp;Participants provided written informed consent before participating in the study. Parental/guardian informed consent forms were obtained for the participants who were younger than 16 years.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent for publication\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNot applicable.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAvailability of data and materials\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe datasets used and/or analyzed during the current study are not publicly available due to including personal information but are available from the corresponding author on reasonable request.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting interests\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare that they have no competing interests.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis study was funded by Asahi Soft Drink Co., Ltd.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthor\u0026rsquo;s contribution\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eJI wrote the manuscript. JI, TS, HM, MT, KK, SY and YS were involved in study design and data interpretation. YY, RN and YH helped to draft the manuscript. All authors read and approved the final manuscript.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAcknowledgements\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis study was performed as part of the Miyagi Sports Medical Projects. It was supported by Asahi Soft Drink Co., Ltd.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eMajewski M, Susanne H, Klaus S. Epidemiology of athletic knee injuries: A 10-year study. The Knee. 2006;13(3):184\u0026ndash;8.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eFuglkj\u0026aelig;r S, Dissing KB, Hestb\u0026aelig;k L. Prevalence and incidence of musculoskeletal extremity complaints in children and adolescents. A systematic review. 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Childhood and adolescent sports-related overuse injuries. Am Fam Physician. 2006;73(6):1014\u0026ndash;22.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003ePatel DR, Villalobos A. Evaluation and management of knee pain in young athletes: overuse injuries of the knee. Transl Pediatr. 2017;6(3):190\u0026ndash;8.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eWu M, Fallon R, Heyworth BE. Overuse Injuries in the Pediatric Population. Sports Med Arthrosc Rev. 2016;24(4):150\u0026ndash;8.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eRathleff CR, Olesen JL, Roos EM, Rasmussen S, Rathleff MS. Half of 12-15-year-olds with knee pain still have pain after one year. Dan Med J. 2013;60(11):A4725.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eIwame T, Matsuura T, Suzue N, Iwase J, Uemura H, Sairyo K. Factors Associated With Knee Pain and Heel Pain in Youth Soccer Players Aged 8 to 12 Years. Orthop J Sports Med. 2019;7(11):2325967119883370.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eJUNGE T, RUNGE L, JUUL-KRISTENSEN B, WEDDERKOPP N. Risk Factors for Knee Injuries in Children 8 to 15 Years: The CHAMPS Study DK. Medicine \u0026amp; Science in Sports \u0026amp; Exercise. 2016;48(4):655\u0026ndash;62.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003ePowell JW, Barber-Foss KD. Sex-related injury patterns among selected high school sports. Am J Sports Med. 2000;28(3):385\u0026ndash;91.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eR\u0026ouml;ssler R, Junge A, Chomiak J, Dvorak J, Faude O. Soccer Injuries in Players Aged 7 to 12 Years: A Descriptive Epidemiological Study Over 2 Seasons. Am J Sports Med. 2016;44(2):309\u0026ndash;17.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eVisnes H, Bahr R. Training volume and body composition as risk factors for developing jumper's knee among young elite volleyball players. Scand J Med Sci Sports. 2013;23(5):607\u0026ndash;13.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eYabe Y, Hagiwara Y, Sekiguchi T, Momma H, Tsuchiya M, Kuroki K, et al. Late bedtimes, short sleeping time, and longtime video-game playing are associated with low back pain in school-aged athletes. Eur Spine J. 2018;27(5):1112\u0026ndash;8.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSekiguchi T, Hagiwara Y, Momma H, Tsuchiya M, Kuroki K, Kanazawa K, et al. Coexistence of Trunk or Lower Extremity Pain with Elbow and/or Shoulder Pain among Young Overhead Athletes: A Cross-Sectional Study. Tohoku J Exp Med. 2017;243(3):173\u0026ndash;8.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eYabe Y, Hagiwara Y, Sekiguchi T, Momma H, Tsuchiya M, Kuroki K, et al. Knee pain is associated with lower back pain in young baseball players: a cross-sectional study. Knee Surg Sports Traumatol Arthrosc. 2019;27(3):985\u0026ndash;90.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eHall R, Barber Foss K, Hewett TE, Myer GD. Sport specialization's association with an increased risk of developing anterior knee pain in adolescent female athletes. J Sport Rehabil. 2015;24(1):31\u0026ndash;5.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eRathleff MS, Rathleff CR, Olesen JL, Rasmussen S, Roos EM. Is Knee Pain During Adolescence a Self-limiting Condition? Prognosis of Patellofemoral Pain and Other Types of Knee Pain. Am J Sports Med. 2016;44(5):1165\u0026ndash;71.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eJayanthi NA, LaBella CR, Fischer D, Pasulka J, Dugas LR. Sports-specialized intensive training and the risk of injury in young athletes: a clinical case-control study. Am J Sports Med. 2015;43(4):794\u0026ndash;801.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eWild CY, Steele JR, Munro BJ. Musculoskeletal and estrogen changes during the adolescent growth spurt in girls. Med Sci Sports Exerc. 2013;45(1):138\u0026ndash;45.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eMorton S, Williams S, Valle X, Diaz-Cueli D, Malliaras P, Morrissey D. Patellar Tendinopathy and Potential Risk Factors: An International Database of Cases and Controls. Clin J Sport Med. 2017;27(5):468\u0026ndash;74.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSaes MO, Soares MCF. Knee pain in adolescents: prevalence, risk factors, and functional impairment. Braz J Phys Ther. 2017;21(1):7\u0026ndash;14.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eKhayambashi K, Ghoddosi N, Straub RK, Powers CM. Hip Muscle Strength Predicts Noncontact Anterior Cruciate Ligament Injury in Male and Female Athletes: A Prospective Study. Am J Sports Med. 2016;44(2):355\u0026ndash;61.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eFord KR, Myer GD, Toms HE, Hewett TE. Gender differences in the kinematics of unanticipated cutting in young athletes. Med Sci Sports Exerc. 2005;37(1):124\u0026ndash;9.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eHewett TE, Myer GD, Ford KR, Heidt RS, Colosimo AJ, McLean SG, et al. Biomechanical Measures of Neuromuscular Control and Valgus Loading of the Knee Predict Anterior Cruciate Ligament Injury Risk in Female Athletes: A Prospective Study. The American Journal of Sports Medicine. 2005;33(4):492\u0026ndash;501.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eYang J, Marshall SW, Bowling JM, Runyan CW, Mueller FO, Lewis MA. Use of discretionary protective equipment and rate of lower extremity injury in high school athletes. Am J Epidemiol. 2005;161(6):511\u0026ndash;9.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLian OB, Engebretsen L, Bahr R. Prevalence of jumper's knee among elite athletes from different sports: a cross-sectional study. Am J Sports Med. 2005;33(4):561\u0026ndash;7.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eMassu\u0026ccedil;a LM, Fragoso I, Teles J. Attributes of Top Elite Team-Handball Players. The Journal of Strength \u0026amp; Conditioning Research. 2014;28(1):178\u0026ndash;86.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eOlsen O-E, Myklebust G, Engebretsen L, Bahr R. Injury Mechanisms for Anterior Cruciate Ligament Injuries in Team Handball:A Systematic Video Analysis. The American Journal of Sports Medicine. 2004;32(4):1002\u0026ndash;12.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eStruzik A, Pietraszewski B, Zawadzki J. Biomechanical analysis of the jump shot in basketball. J Hum Kinet. 2014;42:73\u0026ndash;9.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eBere T, Kruczynski J, Veintimilla N, Hamu Y, Bahr R. Injury risk is low among world-class volleyball players: 4-year data from the FIVB Injury Surveillance System. Br J Sports Med. 2015;49(17):1132\u0026ndash;7.\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"},{"header":"Tables","content":"\u003cp\u003e\u003cstrong\u003eTable 1.\u003c/strong\u003e Baseline characteristics of participants\u003c/p\u003e\n\u003ctable border=\"1\" cellpadding=\"0\" cellspacing=\"0\" width=\"0\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" width=\"14.583333333333334%\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026nbsp;Sports Discipline\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"8.173076923076923%\"\u003e\n \u003cp\u003e\u003cstrong\u003en\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"13.621794871794872%\"\u003e\n \u003cp\u003e\u003cstrong\u003eAge, mean (SD)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"8.493589743589743%\"\u003e\n \u003cp\u003e\u003cstrong\u003eMale, n (%)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"10.256410256410257%\"\u003e\n \u003cp\u003e\u003cstrong\u003eFemale, n (%)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"14.583333333333334%\"\u003e\n \u003cp\u003e\u003cstrong\u003ePractice days per week, mean (SD)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"14.102564102564102%\"\u003e\n \u003cp\u003e\u003cstrong\u003ePractice hours per day (weekdays), mean (SD)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"16.185897435897434%\"\u003e\n \u003cp\u003e\u003cstrong\u003ePractice hours per day (weekends), mean (SD)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" width=\"14.583333333333334%\"\u003e\n \u003cp\u003e\u003cstrong\u003eAll players\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"8.173076923076923%\"\u003e\n \u003cp\u003e7234\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"13.621794871794872%\"\u003e\n \u003cp\u003e10.8 (1.9)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"8.493589743589743%\"\u003e\n \u003cp\u003e5082 (70.3)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"10.256410256410257%\"\u003e\n \u003cp\u003e2152 (29.7)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"14.583333333333334%\"\u003e\n \u003cp\u003e3.3 (1.5)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"14.102564102564102%\"\u003e\n \u003cp\u003e1.9 (1.1)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"16.185897435897434%\"\u003e\n \u003cp\u003e3.7 (2.1)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" width=\"14.583333333333334%\"\u003e\n \u003cp\u003e\u003cstrong\u003eBaseball\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"8.173076923076923%\"\u003e\n \u003cp\u003e1748\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"13.621794871794872%\"\u003e\n \u003cp\u003e10.8 (1.8)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"8.493589743589743%\"\u003e\n \u003cp\u003e1660 (95.0)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"10.256410256410257%\"\u003e\n \u003cp\u003e88 (5.0)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"14.583333333333334%\"\u003e\n \u003cp\u003e3.3 (1.5)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"14.102564102564102%\"\u003e\n \u003cp\u003e1.5 (1.3)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"16.185897435897434%\"\u003e\n \u003cp\u003e5.4 (2.2)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" width=\"14.583333333333334%\"\u003e\n \u003cp\u003e\u003cstrong\u003eFootball\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"8.173076923076923%\"\u003e\n \u003cp\u003e1477\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"13.621794871794872%\"\u003e\n \u003cp\u003e10.3 (1.6)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"8.493589743589743%\"\u003e\n \u003cp\u003e1385 (93.8)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"10.256410256410257%\"\u003e\n \u003cp\u003e92 (6.2)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"14.583333333333334%\"\u003e\n \u003cp\u003e3.1 (1.1)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"14.102564102564102%\"\u003e\n \u003cp\u003e1.7 (0.9)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"16.185897435897434%\"\u003e\n \u003cp\u003e3.0 (1.2)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" width=\"14.583333333333334%\"\u003e\n \u003cp\u003e\u003cstrong\u003eMini-basketball\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"8.173076923076923%\"\u003e\n \u003cp\u003e797\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"13.621794871794872%\"\u003e\n \u003cp\u003e10.3 (1.5)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"8.493589743589743%\"\u003e\n \u003cp\u003e434 (54.5)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"10.256410256410257%\"\u003e\n \u003cp\u003e363 (45.5)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"14.583333333333334%\"\u003e\n \u003cp\u003e3.7 (0.9)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"14.102564102564102%\"\u003e\n \u003cp\u003e2.3 (0.9)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"16.185897435897434%\"\u003e\n \u003cp\u003e3.4 (1.5)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" width=\"14.583333333333334%\"\u003e\n \u003cp\u003e\u003cstrong\u003eVolleyball\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"8.173076923076923%\"\u003e\n \u003cp\u003e681\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"13.621794871794872%\"\u003e\n \u003cp\u003e10.8 (1.8)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"8.493589743589743%\"\u003e\n \u003cp\u003e167 (24.5)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"10.256410256410257%\"\u003e\n \u003cp\u003e514 (75.5)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"14.583333333333334%\"\u003e\n \u003cp\u003e3.4 (1.3)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"14.102564102564102%\"\u003e\n \u003cp\u003e2.3 (1.4)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"16.185897435897434%\"\u003e\n \u003cp\u003e4.0 (2.3)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" width=\"14.583333333333334%\"\u003e\n \u003cp\u003e\u003cstrong\u003eBasketball\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"8.173076923076923%\"\u003e\n \u003cp\u003e680\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"13.621794871794872%\"\u003e\n \u003cp\u003e12.5 (1.6)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"8.493589743589743%\"\u003e\n \u003cp\u003e371 (54.6)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"10.256410256410257%\"\u003e\n \u003cp\u003e309 (45.4)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"14.583333333333334%\"\u003e\n \u003cp\u003e4.8 (1.7)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"14.102564102564102%\"\u003e\n \u003cp\u003e2.2 (0.7)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"16.185897435897434%\"\u003e\n \u003cp\u003e3.6 (1.6)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" width=\"14.583333333333334%\"\u003e\n \u003cp\u003e\u003cstrong\u003eKendo\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"8.173076923076923%\"\u003e\n \u003cp\u003e525\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"13.621794871794872%\"\u003e\n \u003cp\u003e11.0 (2.2)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"8.493589743589743%\"\u003e\n \u003cp\u003e329 (62.7)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"10.256410256410257%\"\u003e\n \u003cp\u003e196 (37.3)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"14.583333333333334%\"\u003e\n \u003cp\u003e3.1 (1.2)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"14.102564102564102%\"\u003e\n \u003cp\u003e2.0 (0.9)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"16.185897435897434%\"\u003e\n \u003cp\u003e1.8 (1.2)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" width=\"14.583333333333334%\"\u003e\n \u003cp\u003e\u003cstrong\u003eJudo\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"8.173076923076923%\"\u003e\n \u003cp\u003e242\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"13.621794871794872%\"\u003e\n \u003cp\u003e11.0 (2.3)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"8.493589743589743%\"\u003e\n \u003cp\u003e178 (73.6)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"10.256410256410257%\"\u003e\n \u003cp\u003e64 (26.4)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"14.583333333333334%\"\u003e\n \u003cp\u003e2.9 (0.9)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"14.102564102564102%\"\u003e\n \u003cp\u003e2.1 (0.6)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"16.185897435897434%\"\u003e\n \u003cp\u003e1.6 (1.1)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" width=\"14.583333333333334%\"\u003e\n \u003cp\u003e\u003cstrong\u003eKarate\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"8.173076923076923%\"\u003e\n \u003cp\u003e236\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"13.621794871794872%\"\u003e\n \u003cp\u003e9.9 (2.2)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"8.493589743589743%\"\u003e\n \u003cp\u003e169 (71.6)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"10.256410256410257%\"\u003e\n \u003cp\u003e67 (28.4)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"14.583333333333334%\"\u003e\n \u003cp\u003e2.4 (1.1)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"14.102564102564102%\"\u003e\n \u003cp\u003e1.9 (0.8)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"16.185897435897434%\"\u003e\n \u003cp\u003e1.8 (1.5)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" width=\"14.583333333333334%\"\u003e\n \u003cp\u003e\u003cstrong\u003eTrack and field\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"8.173076923076923%\"\u003e\n \u003cp\u003e137\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"13.621794871794872%\"\u003e\n \u003cp\u003e10.3 (1.7)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"8.493589743589743%\"\u003e\n \u003cp\u003e57 (41.6)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"10.256410256410257%\"\u003e\n \u003cp\u003e80 (58.4)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"14.583333333333334%\"\u003e\n \u003cp\u003e1.7 (0.9)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"14.102564102564102%\"\u003e\n \u003cp\u003e0.9 (0.9)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"16.185897435897434%\"\u003e\n \u003cp\u003e2.1 (0.6)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" width=\"14.583333333333334%\"\u003e\n \u003cp\u003e\u003cstrong\u003eSoft tennis\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"8.173076923076923%\"\u003e\n \u003cp\u003e128\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"13.621794871794872%\"\u003e\n \u003cp\u003e12.1 (1.9)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"8.493589743589743%\"\u003e\n \u003cp\u003e48 (37.5)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"10.256410256410257%\"\u003e\n \u003cp\u003e80 (62.5)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"14.583333333333334%\"\u003e\n \u003cp\u003e3.7 (1.9)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"14.102564102564102%\"\u003e\n \u003cp\u003e2.0 (0.8)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"16.185897435897434%\"\u003e\n \u003cp\u003e4.4 (2.5)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" width=\"14.583333333333334%\"\u003e\n \u003cp\u003e\u003cstrong\u003eBadminton\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"8.173076923076923%\"\u003e\n \u003cp\u003e123\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"13.621794871794872%\"\u003e\n \u003cp\u003e11. 3 (1.9)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"8.493589743589743%\"\u003e\n \u003cp\u003e39 (31.7)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"10.256410256410257%\"\u003e\n \u003cp\u003e84 (68.3)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"14.583333333333334%\"\u003e\n \u003cp\u003e2.9 (1.1)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"14.102564102564102%\"\u003e\n \u003cp\u003e2.1 (0.7)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"16.185897435897434%\"\u003e\n \u003cp\u003e3.5 (1.7)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" width=\"14.583333333333334%\"\u003e\n \u003cp\u003e\u003cstrong\u003eTable tennis\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"8.173076923076923%\"\u003e\n \u003cp\u003e94\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"13.621794871794872%\"\u003e\n \u003cp\u003e12.8 (1.9)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"8.493589743589743%\"\u003e\n \u003cp\u003e37 (39.4)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"10.256410256410257%\"\u003e\n \u003cp\u003e57 (60.6)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"14.583333333333334%\"\u003e\n \u003cp\u003e3.7 (1.9)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"14.102564102564102%\"\u003e\n \u003cp\u003e2.3 (0.8)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"16.185897435897434%\"\u003e\n \u003cp\u003e2.9 (1.8)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" width=\"14.583333333333334%\"\u003e\n \u003cp\u003e\u003cstrong\u003eHandball\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"8.173076923076923%\"\u003e\n \u003cp\u003e41\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"13.621794871794872%\"\u003e\n \u003cp\u003e11.2 (2.3)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"8.493589743589743%\"\u003e\n \u003cp\u003e24 (58.5)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"10.256410256410257%\"\u003e\n \u003cp\u003e17 (41.5)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"14.583333333333334%\"\u003e\n \u003cp\u003e3.3 (2.0)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"14.102564102564102%\"\u003e\n \u003cp\u003e2.7 (0.4)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"16.185897435897434%\"\u003e\n \u003cp\u003e3.3 (0.8)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" width=\"14.583333333333334%\"\u003e\n \u003cp\u003e\u003cstrong\u003eSwimming\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"8.173076923076923%\"\u003e\n \u003cp\u003e41\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"13.621794871794872%\"\u003e\n \u003cp\u003e9.9 (2.0)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"8.493589743589743%\"\u003e\n \u003cp\u003e29 (70.7)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"10.256410256410257%\"\u003e\n \u003cp\u003e12 (29.3)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"14.583333333333334%\"\u003e\n \u003cp\u003e2.4 (1.4)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"14.102564102564102%\"\u003e\n \u003cp\u003e1.2 (0.5)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"16.185897435897434%\"\u003e\n \u003cp\u003e1.0 (1.0)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" width=\"14.583333333333334%\"\u003e\n \u003cp\u003e\u003cstrong\u003eOthers\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"8.173076923076923%\"\u003e\n \u003cp\u003e284\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"13.621794871794872%\"\u003e\n \u003cp\u003e11 (2.3)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"8.493589743589743%\"\u003e\n \u003cp\u003e155 (54.6)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"10.256410256410257%\"\u003e\n \u003cp\u003e129 (45.4)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"14.583333333333334%\"\u003e\n \u003cp\u003e2.4 (1.6)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"14.102564102564102%\"\u003e\n \u003cp\u003e1.7 (0.8)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"16.185897435897434%\"\u003e\n \u003cp\u003e2.7 (2.0)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003eSD, standard deviation.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eTable 2.\u0026nbsp;\u003c/strong\u003eAssociation between sports discipline and knee pain in multivariate analysis\u003c/p\u003e\n\u003ctable border=\"1\" cellpadding=\"0\" cellspacing=\"0\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" width=\"44.411764705882355%\"\u003e\n \u003cp\u003e\u003cstrong\u003eVariables\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"55.588235294117645%\"\u003e\n \u003cp\u003e\u003cstrong\u003eAdjusted OR (95% CI)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" width=\"44.411764705882355%\"\u003e\u003cbr\u003e\u003c/td\u003e\n \u003ctd valign=\"top\" width=\"55.588235294117645%\"\u003e\u003cbr\u003e\u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" width=\"44.411764705882355%\"\u003e\n \u003cp\u003e\u003cstrong\u003eFootball\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"55.588235294117645%\"\u003e\n \u003cp\u003e1.00\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" width=\"44.411764705882355%\"\u003e\n \u003cp\u003e\u003cstrong\u003eHandball\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"55.588235294117645%\"\u003e\n \u003cp\u003e2.27 (0.95\u0026ndash;5.42)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" width=\"44.411764705882355%\"\u003e\n \u003cp\u003e\u003cstrong\u003eMini-basketball\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"55.588235294117645%\"\u003e\n \u003cp\u003e1.90 (1.44\u0026ndash;2.52)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" width=\"44.411764705882355%\"\u003e\n \u003cp\u003e\u003cstrong\u003eBasketball\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"55.588235294117645%\"\u003e\n \u003cp\u003e1.62 (1.20\u0026ndash;2.18)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" width=\"44.411764705882355%\"\u003e\n \u003cp\u003e\u003cstrong\u003eBadminton\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"55.588235294117645%\"\u003e\n \u003cp\u003e1.21 (0.67\u0026ndash;2.17)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" width=\"44.411764705882355%\"\u003e\n \u003cp\u003e\u003cstrong\u003eVolleyball\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"55.588235294117645%\"\u003e\n \u003cp\u003e1.06 (0.75\u0026ndash;1.49)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" width=\"44.411764705882355%\"\u003e\n \u003cp\u003e\u003cstrong\u003eTrack and field\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"55.588235294117645%\"\u003e\n \u003cp\u003e0.97 (0.47\u0026ndash;2.01)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" width=\"44.411764705882355%\"\u003e\n \u003cp\u003e\u003cstrong\u003eJudo\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"55.588235294117645%\"\u003e\n \u003cp\u003e0.94 (0.56\u0026ndash;1.58)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" width=\"44.411764705882355%\"\u003e\n \u003cp\u003e\u003cstrong\u003eTable tennis\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"55.588235294117645%\"\u003e\n \u003cp\u003e0.73 (0.37\u0026ndash;1.46)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" width=\"44.411764705882355%\"\u003e\n \u003cp\u003e\u003cstrong\u003eSoft tennis\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"55.588235294117645%\"\u003e\n \u003cp\u003e0.70 (0.37\u0026ndash;1.31)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" width=\"44.411764705882355%\"\u003e\n \u003cp\u003e\u003cstrong\u003eKendo\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"55.588235294117645%\"\u003e\n \u003cp\u003e0.62 (0.41\u0026ndash;0.95)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" width=\"44.411764705882355%\"\u003e\n \u003cp\u003e\u003cstrong\u003eBaseball\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"55.588235294117645%\"\u003e\n \u003cp\u003e0.48 (0.36\u0026ndash;0.65)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" width=\"44.411764705882355%\"\u003e\n \u003cp\u003e\u003cstrong\u003eKarate\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"55.588235294117645%\"\u003e\n \u003cp\u003e0.44 (0.20\u0026ndash;0.96)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" width=\"44.411764705882355%\"\u003e\n \u003cp\u003e\u003cstrong\u003eSwimming\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"55.588235294117645%\"\u003e\n \u003cp\u003e0.32 (0.04\u0026ndash;2.35)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" width=\"44.411764705882355%\"\u003e\n \u003cp\u003e\u003cstrong\u003eOthers\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"55.588235294117645%\"\u003e\n \u003cp\u003e1.21 (0.74\u0026ndash;1.96)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003eAdjusted for sex, age, training days per week, and training hours per weekday and per weekend. OR, odds ratio; CI, confidence interval.\u003c/p\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"bmc-sports-science-medicine-and-rehabilitation","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"ssmr","sideBox":"Learn more about [BMC Sports Science, Medicine and Rehabilitation](http://bmcsportsscimedrehabil.biomedcentral.com/)","snPcode":"","submissionUrl":"https://www.editorialmanager.com/ssmr/default.aspx","title":"BMC Sports Science, Medicine and Rehabilitation","twitterHandle":"BMC_series","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"em","reportingPortfolio":"BMC Series","inReviewEnabled":true,"inReviewRevisionsEnabled":true},"keywords":"knee pain, young sports players, sports discipline","lastPublishedDoi":"10.21203/rs.3.rs-1699129/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-1699129/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003e\u003cstrong\u003eBackground\u003c/strong\u003e\u003c/p\u003e\u003cp\u003eKnee pain is a common symptom among young sports players. Nevertheless, few studies with large sample size have been published reporting the difference of the prevalence of knee pain for each sport among young sports players.\u003c/p\u003e\u003cp\u003e\u003cstrong\u003eMethods\u003c/strong\u003e\u003c/p\u003e\u003cp\u003eThis study was to investigate the point prevalence of knee pain according to age, sex and sports discipline and the association between knee pain and sports discipline among young sports players. A cross-sectional study was conducted using a self-reported questionnaire on young sports players aged 6–15 years who belonged to the Miyagi Amateur Sports Association. Multivariable logistic regression models were used to examine the association between knee pain and sports discipline and were adjusted for age, sex, training days per week, and training hours per weekday and weekend.\u003c/p\u003e\u003cp\u003e\u003cstrong\u003eResults\u003c/strong\u003e\u003c/p\u003e\u003cp\u003eA total of 7234 young sports players were included. The point prevalence of knee pain was 10.9%. Females (13.3%) had more knee pain than males (9.8%). 13 years had the highest prevalence of knee pain (19.1%). In multivariable analysis, mini-basketball (odds ratio, 1.90; 95% CI, 1.44–2.52) and basketball (odds ratio, 1.62; 95% CI, 1.20–2.18) were significantly associated with knee pain, compared with football. \u003c/p\u003e\u003cp\u003e\u003cstrong\u003eConclusion\u003c/strong\u003e\u003c/p\u003e\u003cp\u003eThe prevalence of knee pain among young athletes differed according to age, sex, and sports discipline. Their parents and clinicians should recognize this information to manage knee pain prevention among young sports players.\u003c/p\u003e","manuscriptTitle":"Knee pain in young sports players aged 6 to 15 years: a cross-sectional study in Japan","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2022-06-06 14:46:58","doi":"10.21203/rs.3.rs-1699129/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Major revision","date":"2022-06-24T16:21:30+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2022-06-18T14:11:30+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"7ef1ba07-f5fe-42d0-910f-b8d648502682","date":"2022-06-06T12:52:28+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2022-06-05T01:20:40+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2022-06-05T01:13:51+00:00","index":"","fulltext":""},{"type":"editorInvited","content":"","date":"2022-06-04T11:29:18+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2022-06-04T11:26:48+00:00","index":"","fulltext":""},{"type":"submitted","content":"BMC Sports Science, Medicine and Rehabilitation","date":"2022-05-27T08:48:13+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"bmc-sports-science-medicine-and-rehabilitation","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"ssmr","sideBox":"Learn more about [BMC Sports Science, Medicine and Rehabilitation](http://bmcsportsscimedrehabil.biomedcentral.com/)","snPcode":"","submissionUrl":"https://www.editorialmanager.com/ssmr/default.aspx","title":"BMC Sports Science, Medicine and Rehabilitation","twitterHandle":"BMC_series","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"em","reportingPortfolio":"BMC Series","inReviewEnabled":true,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"2bd3981c-a474-4f63-ad81-143ac8cb4a71","owner":[],"postedDate":"June 6th, 2022","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[],"tags":[],"updatedAt":"2023-10-16T18:51:45+00:00","versionOfRecord":{"articleIdentity":"rs-1699129","link":"https://doi.org/10.1186/s13102-022-00606-y","journal":{"identity":"bmc-sports-science-medicine-and-rehabilitation","isVorOnly":false,"title":"BMC Sports Science, Medicine and Rehabilitation"},"publishedOn":"2023-02-07 18:46:26","publishedOnDateReadable":"February 7th, 2023"},"versionCreatedAt":"2022-06-06 14:46:58","video":"","vorDoi":"10.1186/s13102-022-00606-y","vorDoiUrl":"https://doi.org/10.1186/s13102-022-00606-y","workflowStages":[]},"version":"v1","identity":"rs-1699129","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-1699129","identity":"rs-1699129","version":["v1"]},"buildId":"uwybb5PU2iWlRI8EIam5Y","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}