Step-to-Step Variability in Tibiofemoral Contact Force During Walking Measured by an Instrumented Knee Implant

Understanding the dynamic loading at the knee can provide critical information for characterizing normal as well as pathologic conditions. However, measuring or predicting this loading from extrinsic measurement remains an unmet challenge. Part of the complexity of generalizing the tibiofemoral loading is that contact force patterns are largely subject specific and vary within subjects based on the activity performed and the specific muscle activation patterns exhibited [1]. While several studies have quantified the intra-subject variability in extrinsic knee kinematics and kinetics during repetitive activities of daily living [2,3], changes in patterns of muscle contraction can yield substantial step-to-step variability in tibiofemoral contact force with minimal changes in extrinsic kinetics due to the potential influence of muscle co-contraction. Knowledge of this step-to-step tibiofemoral loading variability could play an integral role in improving the interpretation of analytical contact force predictions.