The contact surfaces of wide-spread applied human knee joint prostheses can be described with simple geometrical elements. The relative motion realized by knee joint is ensured by complicated condyle surfaces. For this reason the implanted prostheses comply with requirements limited and it causes additional load on the diseased bony tissue. In order to describe the motion of knee joint at first the authors constrained coordinate-systems on the basis of anatomical landmarks to the femur and tibia and then they joined a three-cylindrical mechanism as mechanical model to the axes of coordinate-systems. In the second phase ‘the’ authors determined the six independent kinematical parameters of tibia compared to the fixed femur during flexion and extension. The experimental examinations were carried out on cadaver knees. The positioning was tracked by optical positioning appliance. Needed parameters can be obtained from the recorded data determined by the applied kinematical model.
Considering the irregular shapes of femur and tibia the anatomical coordinate systems can be joined with 1-2 mm and 2-4 degree position deflections. The aim of this paper is the determination of the effects of position deflections on kinematical parameters.