A hip replacement uses the combination of metal gliding on plastic, and cement to attach the artificial components to the bone. The arthritic head of the femur is removed and replaced with a metal ball which is attached to a metal stem. The stem is cemented into the hollow marrow space of the femur. The worn out hip socket is lined with a plastic cup, which is also cemented in place.

The painful parts of the arthritic hip are thereby completely replaced with metal and plastic surfaces. The plastic socket has a very low frictional resistance, and a very low wear rate against the metal ball.

With the development of the Cementless Hip Replacement the surface of the metal parts is porous, and looks like coral, hence bone can grow into the metal pores and lock the implant into place without the use of cement.