A biocompatible prosthetic device comprising a thin low friction spacer for location to overlie a bone member in an interpositional location between opposed bone joint articular surfaces. The prosthesis is preferably a thin spacer with at least one low friction surface, the spacer being adapted for location about a bone member in an interpositional location between opposed bone joint articular surfaces preferably about a margin of articular cartilage of a bone member's condyle, preferably without any modification of the articular surface of the condyle. One preferred use of a prosthesis is in a human temporomandibular joint as a thin cap-like member fitted closely over the mandibular condyle to be disposed intermediate of the mandibular condyle and the mandibular fossa of the temporomandibular joint.