Joint forces in extension of the knee: Analysis of a mechanical model

Abstract

A two-dimensional model of the tibio-femoral joint was constructed by using the results of cadaver knee dissections together with radiographic landmarks on healthy knees loaded at various angles of flexion. The tibiofemoral compressive force during isometric knee extension had the same magnitude as the patellar tendon force. The tibio-femoral shear force changed direction from posterior at full flexion to anterior when the knee was extended, indicating that high forces may arise in the anterior cruciate ligment in the straight knee. Women developed some 20 per cent higher knee joint forces than men for the same extending muscular moment, since women''s patellar tendon moment arms were found to be shorter. The model presented may be used for quantifying tibio-femoral forces during knee extending activities.