Multi-body system model of the knee joint and its applications

A basic task in biomechanics is the precise analysis of human movements and the investigation of muscle forces that are responsible for these movements. When using inverse dynamics with a focus on the lower extremities, the knee model type is of major interest, as it is well known that the calculated muscle forces depend on the knee model type. It is essential to use individually parameterized models for the knee joint as well as for the femoropatellar joint while analysing the correlations between external and internal loads and the efficiency of specific training exercises for the lower extremities. It will be shown that different knee model types and femoropatellar model types have a major influence on calculated muscle forces. Within this study the multi-body system model was applied to leg extension movements performed on a leg press machine. Concerning the adjustment of a leg press machine, the following two questions were considered: How should a leg press machine be adjusted for individual exercises taking into account the minimization of knee strain? Does the muscular strain correspond to the load calculated and applied externally? The results of this application show that the knee strain could be reduced by 10% after simulative variation of the boundary conditions given by the leg press machine.