Lines of action and moment arms of the major force-bearing structures crossing the human knee joint: comparison between theory and experiment.

Lines of action and moment arms in the sagittal plane of the major tension-bearing structures at the knee joint were calculated using an anatomy-based mathematical model and compared with experimental measurements reported by Herzog & Read (1993). The mobility of the model tibiofemoral joint was controlled by a sagittal plane 4-bar linkage consisting of the femur, tibia and the 2 cruciate ligaments while the knee extensor mechanism was characterised by a patellofemoral joint model. Model parameters were obtained from previous cadaveric and MRI studies. The theoretical results compare well with the published experimental measurements which suggests that, with relatively simple measurements, the model was able to reproduce major features of the natural knee joint and provide necessary information for further mechanical analysis.