A three-dimensional geometric model of the knee for the study of joint forces in gait

A geometric model has been developed to predict the kinematics of the knee from the geometry of its anatomical structures. This model has two important applications in gait analysis. First, it predicts the lines of action of the forces through the anterior cruciate ligament, posterior cruciate ligament, medial collateral ligament and at articular contact in the medial and lateral compartments. Second, it predicts the changing position and orientation of the axis of rotation of the knee. In an illustration of its potential, a preliminary version of the model successfully predicted the patterns of tibial rotation and axis orientation that have been observed in experimental studies of normal gait. Once it has been quantitatively validated and refined, the model will be a useful tool in gait analysis, with particular applications in the estimation of forces through the muscles, ligaments and at articular contact in the knee and in the calculation of joint powers.