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. Thus this study shows a present situation about diagnostic tool for knee OA. We propose the method to establish diagnostic tool for knee OA from gait pattern and models.