Biomechanics and gait analysis in total knee replacement.

A primary goal of total knee replacement has been the relief of pain. As new implant designs evolve and other improvements take place, we must broaden our goals to include increased longevity and an improvement in patient function, especially among younger patients. There is a relationship between the longevity of the implant and patient function, since function determines loads on the joint and the motion of the joint. In addition, ultimate breakdown of the prosthesis depends upon these same loads. This paper will first discuss the relationship between function and some of the intrinsic mechanics of the knee joint, and then the relationship between function and mechanics and the longevity of the implant. It is based on an analysis of patients with a variety of differently designed total knee replacements that replicate, to a greater or lesser degree, the anatomy of the knee joint. Some of the implants sacrifice both anterior and posterior cruciates, and some retain both.