orthopedic implants of zirconium or zirconium - based alloy coated with blue or blue - black zirconium oxide or zirconium nitride to provide low friction , highly wear resistant coatings especially useful in artificial joints , such as hip joints , knee joints , elbows , etc . the invention zirconium oxide or nitride coated prostheses are also useful in that the coatings provide a barrier against implant corrosion caused by ionization of the metal prosthesis . such protection can be extended by the use of oxidized or nitrided porous coatings of zirconium or zirconium alloy beads or wire mesh into which bone spicules may grow so that the prosthesis may be integrated into the living skeleton .