Human gait analysis using multibody dynamics and contact modeling

The objectives of this thesis research are: (1) to develop a new 3-D computational gait model, (2) to develop a contact model for the knee joint considering the effect of sliding and rolling, ligaments and tendons, (3) to develop a methodology for gait experimental validation, (4) to develop a technique for evaluating ligaments strain around the femoraltibia knee joint.; The accuracy of the computational model is highly dependent on the accuracy of the input data sets. The gait trial and standing data sets were collected from a commercial optical experimental technique that was generally available in the gait laboratory. However, representative geometry for the knee joint and representative ligament locations around the femoraltibia knee joint were used because of experimental limitations.; In previously published contact model studies, the contact force between femoral condyle and tibia surface was based on the depth of penetration and the relative velocity normal to the contact surface, while friction forces are calculated based upon the relative velocities tangential to the surface. However, it is shown that this method is not applicable to be used in the gait analysis.; The Average Coordinate Reference System (ACRS) method was developed. Using this methodology the error could be reduced about 40% compared to general Euler angle method used in gait analysis for the same subject. Using the combination of ACRS and discretized joint geometry, the results was improved about 400% compared to the general Euler angle method.; Ligament strains were determined using the computational model developed in this thesis. Results of this research compare favorably with the published literature.; The lateral and medial condyle contact forces were determined from the total internal forces of the knee joint and the twelve ligament reaction forces. In order to solve this problem, a least square method was used.; In order to verify the generality of the model and to check the possibility of clinical application of the methodology an ACL injured subject was tested. And results are compared to healthy subject data.