Sex Differences in Knee Flexion Angle During a Rapid Change of Direction While Running

Background:Females experience greater overall rates of athletic anterior cruciate ligament (ACL) injury than males. The specific mechanisms of the predisposition remain unclear.Hypothesis:Modeling of knee kinematics has shown that the more extended the knee joint, the greater the strain on the ACL. The authors hypothesized that female athletes would have a lesser degree of knee flexion than male athletes at initial ground contact while performing change-of-direction cutting maneuvers.Study Design:Controlled laboratory study.Methods:Twenty female and 20 male high school soccer athletes with at least 1 year of experience were recruited for the study. Athletes were excluded if they had a history of any major lower limb injury or current knee pain causing a reduction in training and/or competition. Reflective markers were attached at the greater trochanter of the femur, the lateral epicondyle of the knee, and the lateral malleolus of the ankle to enable motion capture. Each athlete performed 6 change-of-direc...