Background: Insufficient hip flexibility, a limiting factor for lower extremity rotation, can cause great rotational stress and consequent injury to the knees and ankles. A limited range of motion (ROM) of the hip might be associated with increased risk of non-contact anterior cruciate ligament (ACL) injury. We investigated the association between the risk of non-contact ACL injured student athletes and limitations of hip ROM.
Methods: A case-control study was conducted at an orthopaedic clinic in Japan. Cases included all patients with non-contact ACL injury and without known marked alignment abnormalities who visited the orthopaedic clinic during 2000-2008. Controls included all patients with non-ACL sports-related injuries who visited the same clinic in 2000. The adjusted odds ratio of ROM of the hip was evaluated for non-contact ACL injury risk.
Results: These cases were 44 ACL cases and 123 controls aged 13-17 years. The odds ratios (ORs) of internal and external rotations of hip ROMs were adjusted for age, sex, BMI, type of sports and hip ROM (flexion, extension, adduction, abduction). The adjusted ORs for a 10° increase of the sum of the right and left internal hip rotations were 0.18 (95% confidence interval [CI], 0.10-0.34, p<0.0001), and 0.23 (95% CI, 0.14-0.39, p<0.0001) for external rotations, and the observed ORs were small.
Conclusions: Data obtained from this small sample indicate that limited hip rotation ROMs in young athletes have the possibility of association with increased risk of non-contact ACL injury.
Level of evidence: III - case-control study.
Keywords: ACL; Flexibility; ROM; Risk factor.