Knee osteoarthritis (OA) becomes a major public issue, but a strategy to prevent the disease has not established yet due to lack of an accurate method to measure an internal motion of the knee of individual patients. Therefore mechanical engineering model and a standard of evaluation of the disease is needed to improve the situation. Currently, there are a few studies to develop the model including allowance of joint movement and ligaments. Thus this study shows the model accuracy by forward dynamics and discusses the result of inverse dynamics of various gait patterns. As a result, it can be confirmed that ligaments are more effective than muscles around knee joint with our various models. In addition we propose the important factor of knee OA from gait pattern and models.