Perturbation training improves knee kinematics and reduces muscle co-contraction after complete unilateral anterior cruciate ligament rupture

Background and Purpose. Dynamic knee stabilization strategies of people who successfully compensate for the absence of an anterior cruciate ligament (ACL) (copers) are different from those of people who do not compensate well for the injury (noncopers). Early after injury, certain patients (potential copers) can increase the likelihood of successfully compensating for the injury by participating in 10 sessions of perturbation training. The purpose of this study was to determine how perturbation training alters muscle co-contraction and knee kinematics in potential copers. Subjects. Seventeen individuals with acute, unilateral ACL rupture who were categorized as potential copers and 17 subjects without injuries who were matched by age, sex, and activity level were recruited for this study. Methods. Motion analysis and electromyographic data were collected as subjects walked across a stationary or moving platform (horizontal translation) before and after perturbation training. Results. Before training, potential copers had higher co-contraction indexes and lower peak knee flexion angles than subjects without injuries. After training, potential copers' movement patterns more closely resembled those of subjects without injuries (ie, they showed reduced co-contraction indexes and increased peak knee flexion angles during stance). Discussion and Conclusion. Perturbation training reduced quadriceps femoris-hamstring muscle and quadriceps femoris-gastrocnemius muscle co-contractions and normalized knee kinematics in individuals with ACL rupture who were classified as potential copers. Findings from this study provide evidence for a mechanism by which perturbation training acts as an effective intervention for promoting coordinated muscle activity in a select population of people with ACL rupture.