an orthopedic implant with a diffusion - hardened surface on non - load bearing areas of the implant for interaction with non - load bearing surfaces of a polymeric bio - compatible material , such as uhmwpe . the orthopedic implant is a posterior stabilized knee prosthetic and system where a coating of oxidized zirconium is formed in the cam of the femoral prosthetic for interaction with the central post of a polymeric tibial insert . the diffusion - hardened surface of the orthopedic implant provides a strengthened cam and reduction in wear in the central post of the polymeric tibial insert .