The purpose of this study was to evaluate the occurrence of bone ingrowth in a porous coated tibial component of a canine total condylar design knee replacement model. The entire undersurface of the tibial prosthesis was covered by a titanium fiber metal porous composite pad. Projecting from this surface were three short, cylindrical, fiber metal coated pegs that along with a posterior screw provided initial stabilization of the device. Left total knee replacements were performed on six dogs using alignment and cutting jigs to prepare the bony surfaces. The dogs were killed 6 months following surgery. Extensive bone ingrowth was present in all pegs of every tibial component. Bone ingrowth was present in 12% of the pad area of one component, 22.7 to 41.6% in four components, and 81.1% in another. The void spaces in other areas were filled with fibrous tissue or in the periphery of the device with fibrocartilage. Bone ingrowth in the pad was consistent in the vicinity of the pegs and was variable in regions not adjacent to the pegs, suggesting that the pegs exerted a strong influence on the pattern of bone ingrowth into the pad.