Youth Baseball Players with Elbow and Shoulder Pain Have Both Low Back and Knee Pain: A Cross-sectional Study

OBJECTIVES: Serious arm injuries in youth baseball players have been increasing. Though a breakage in the kinetic chain could affect arm injuries, an association between arm injuries and insufficient support of the trunk and lower extremities have not been well understood. The purpose of this study was to investigate the association of low back and knee pain with elbow and/or shoulder complaints among youth baseball players. METHODS: Study participants were mostly school-aged athletes belonging to Junior Sports Club Association of Miyagi prefecture (aged 6 to 15 years old). A self-administered questionnaire and informed consent document were mailed to25,469 registered athletes. Of those, 7,333 athletes replied both written informed consent and questionnaire (response rate was 28.8%). Those who did not play baseball (n = 5,577) and played both baseball and the other sports (n = 26) were excluded from this study. Missing data on variables (n = 192) were also excluded. The final study population was comprised of 1,535 players. We used multiple logistic regression analysis to examine the association of low back and knee pain with elbow and/or shoulder pain. Variables considered in the models were sex, age, BMI, years of athletic experience, position, team level, the amount of practice, participating day in team practice and game per week, frequency of participation in games, and practice intensity. RESULTS: The frequency of elbow and/or shoulder pain was 24.8% (n= 393); that of elbow pain, 14.3% (n = 226); that of shoulder pain, 17.3 % (n = 273); that of both elbow and shoulder pain, 6.6% (n = 105); and that of low back and knee pain were 8.4% (n= 134) and 13.1% (n = 208), respectively. The frequency of elbow and/or shoulder pain who had low back and knee pain were 61.2% (n = 82) and 51.9% (n= 108) (p<0.001), respectively. The presence of low back and knee pain were strongly associated with elbow and/or shoulder pain (adjusted ORs (95%CI): 4.23 (2.83 - 6.34), p<0.001 and 3.11 (2.24 - 4.31), p<0.001, respectively), elbow (adjusted ORs (95%CI): 3.19 (1.74 - 5.83), p<0.001 and 2.45 (1.47 - 4.07), p=0.001, respectively), shoulder (adjusted ORs (95%CI): 4.25 (2.59 - 7.29), p<0.001 and 3.31 (2.17 - 5.05), p<0.001, respectively), and both elbow and shoulder pain (adjusted ORs (95%CI): 5.49 (3.08 - 9.79), p<0.001 and 3.52 (2.12 - 5.85), p<0.001, respectively). CONCLUSION: Both low back and knee pain were significantly associated with elbow and/or shoulder pain in youth baseball players. This result suggests that checking the trunk and lower extremities as well as elbows and shoulders are important for preventing sever injuries in youth baseball players.