Quasistatic model of the knee during exercises

A planar quasistatic analytical model of the knee joint was developed, taking into account the muscle activities during knee exercises, lines of action of muscle groups and cruciate ligaments. Tibiofemoral, patellofemoral compressive forces and cruciate ligaments´ tensions were determined by using resultant force and torque at the knee and muscle forces estimated by the model with the orientations and lever arms of the muscles and ligaments selected from the literature. An optimization program was used to minimize the errors caused by the estimation of the muscle forces. The model was used in a ten-subject study of open and closed kinetic chain exercises. In this study, resultant force and torque at the knee during exercise were determined by a three-dimensional motion analysis system and a kinetic model using the principles of inverse dynamics. It was concluded that the predictions of the model agreed well with experiments described in the literature.