This article reviews the problem of ultrahigh molecular weight polyethylene component surface degradation in total hip and total knee prostheses, including its clinical implications. Several factors affecting surface damage have been identified from a combination of the observations of in-vivo degradation made on retrieved components, experimental measurement of contact stresses on polyethylene components as a result of contact with their metallic counterpart, and analytical studies of both contact stress and the stresses beneath the polyethylene surface. Both the observations of in-vivo surface degradation and the analytical studies demonstrate that surface degradation is a more severe problem in total knee replacements than in total hip replacements. The performance of polyethylene components, as affected by design factors such as material thickness and material modification, is also considered.