Abstract: An orthopedic device having a protective coating bonded to the substrate material of the device. The protective coating includes a thin layer of tetrahedral bonded Carbon (ta-C). The substrate also optionally includes an interface layer to facilitate the initial bonding and retention of the ta-C layer. The ta-C layer has a concentration of sp3 bonded carbon which varies through its thickness, such as varying in individual layers forming the protective coating. The protective coating may also be doped with various materials, either through its thickness, or at either an inner or an outer interface, or both, or include ion diffusion barriers.