Predictors Of Knee Valgus Angle During A Jump-landing Task

Abstract

Excessive knee valgus has been described as a potential risk factor for anterior cruciate ligament (ACL) injury. Thus, it is important to understand factors that may influence knee valgus. PURPOSE To determine the influence of hip motion (adduction and rotation) and muscle strength on knee valgus during a jump-landing task. METHODS A total 117 participants took part in this study (males=63, females=54). Participants performed a jump-landing task by jumping from a 30-cm high box. Following the initial landing the participants immediately jumped upward for maximal vertical height. During the jumplanding task the angles at initial contact and peak were measured for knee valgus, hip adduction and hip rotation. An electromagnetic tracking system was used to measure joint kinematics. A hand-held dynamometer was used to assess the strength of the following muscles: gluteus maximus, gluteus medius, hip external rotators, hip internal rotators, quadriceps, and hamstrings. Pearson product-moment correlations were performed between each of the joint kinematics and muscle strength variables. Separate forward stepwise multiple regression analyses were performed to determine the relationship for knee valgus at initial contact and peak knee valgus with hip kinematics and muscle strength variables. RESULTS Statistical analyses involving muscle strength revealed significant relationships between knee valgus at initial contact and peak knee valgus with strength of the quadriceps, gluteus maximus, hip external rotators, and gluteus medius muscles (P<.05). Regression analyses revealed that only gluteus medius strength was a significant predictor of knee valgus at initial contact (R2=.06, P<.05) and peak knee valgus (R2=.07, P<.05), although this may be considered low predictive power. Statistical analyses involving hip kinematics also revealed significant relationships between knee valgus at initial contact and peak knee valgus (P<.05). Regression analyses revealed that both hip adduction and hip rotation were significant predictors of knee valgus at initial contact (R2 = .67, P<.05) and peak knee valgus (R2=.48, P<.05). CONCLUSIONS Individuals with greater hip adduction and rotation and reduced gluteus medius strength demonstrated greater knee valgus. These findings demonstrate the importance of hip motion and strength for controlling knee valgus. This may have implications in understanding ACL injury risk factors injury and in the design of ACL injury prevention programs. (Funded by the American Orthopaedic Society for Sports Medicine)