Finite element contact analysis of the hip joint.

The hip joint plays an important role in the musculoskeletal system; however, current knowledge of the mechanics of the hip joint, especially with regard to the distribution of stress, remains limited. In experimental research, difficulties arise during reproduction of physiological conditions of daily activities and practicable measurement of locations inside the hip joint without violating the physiological environment. On the other hand, numerical approaches, such as finite element analysis, have become useful tools in the field of biomechanics. In finite element contact analysis of the hip joint, due to discretization of contact surfaces, computational instability might occur when the contact nodes move near the edges of the contact elements. In this study, to overcome this problem, a contact smoothing approach was introduced by applying Gregory patches. Contact analysis of the hip joint was then performed for three representative daily activities; i.e., walking, rising up from a chair and knee bending. The effectiveness of the adopted smoothing approach was verified by comparing the results with those obtained experimentally. The distribution and history of contact stress, which have heretofore been scarcely reported, were also obtained and the implications associated with osteoarthritis were discussed.