Mechanisms of compensating for anterior cruciate ligament deficiency during gait

Introduction: The quadriceps avoidance gait pattern may not be as common in ACL deficient (ACLd) gait as previously described. Purpose: The purpose of this study was to investigate the existence of the quadriceps avoidance pattern in ACL deficient patients and to further identify gait compensations that may exist in this subject pool. Methods: In the present study, hip, knee, and ankle gait kinematics, and kinetics and thigh EMG profiles were recorded and compared for 16 ACLd and 8 control subjects. Results: The quadriceps avoidance gait pattern was not observed for any of the subjects. Hip, knee, and ankle kinematics and kinetics were not different between groups. However, nine ACLd subjects (group A) demonstrated a normal biphasic knee moment pattern, whereas seven (group 13) demonstrated an all knee extensor pattern. This indicates different adaptive mechanisms may be present in ACLd gait. Group A exhibited a hip strategy that increased hip extensor output, decreased knee extensor output, and allowed normal knee kinematics. Group B demonstrated a knee strategy that increased the stiffness of the joint and utilized a flexed knee gait. Conclusion: The prevalence of multiple adaptive strategies to compensate for ACL deficiency has several important ramifications. First, an ACLd subject pool with mixed compensating strategies may deter the identification of specific coping mechanisms and account for the confounding results in the literature. Second, the importance of the hip extensors should not be overlooked when studying this population.