Abstract:
The knee is one of the most complex joints in the human body and more likely to be injured than any other. While most human joints move with a static rotational axis, the knee's axis o rotation relocates during flexion-extension movement resulting in an overlap of rolling and gliding motion in the joint. Determining the paths of motion and consequently the resulting pressures and contact forces in the knee compartment due to tibiofemoral articulation during gait is extremely useful for planning clinical procedures and in designing knee braces and implants. While previous two-dimensional knee models based on four-bar-mechanisms have been proven to be useful, but wrong due to neglecting several aspects of knee motion, three -dimensional models have been developed in recent computer simulations. These modelling works are often based on one individual data set and contain many assumptions and constraints. The research presented here is based on the four-bar-linkage (4BL) mechanism. While the model is approached in two dimensions, it is later advanced to three dimensions. The four links are representing the knee's cruciate ligaments as well as the tibial and femoral condyle's surfaces. All the mechanism's links are at first considered as one-line rigid bars and in the model considered vectors. The three- dimensional model includes the physiological orientation of the cruciate ligaments and the screw-home mechanism. With the input variable being the flexion-extension angle of the knee, the dynamic model will eventually also include the ligament wrapping of the posterior cruciate ligament around the posterior edge of the tibial condyle. Showing in a quantitative and qualitative approach that the resulting motion of the tibial condyle towards the femoral condyle does not coincide with the physiological shape of the condyles of the CMISS model, the necessity arises to include non-rigid links. Eventually, the change of length of the ligaments depending on the angle of flexion and extension rounds the model o . To the author's knowledge, a model which is based on a four-bar linkage, but includes three-dimensions as well as significant mechanisms of the knee joint, such as screw-home, has until completion of this thesis not been published.