A noncemented and clinically stable porous-coated patellar component (PCATM) was removed from a patient after 11 months because of infection. It was sectioned and examined histologically in undecalcified, thin-ground sections. The bone ingrowth into the porous space was measured at eight levels. Each histologic section was quantified by a conventional point-counting method using a square grid.There was inhomogeneous, but extensive, bone ingrowth, often extending to the core of the patellar component, with direct contact between bone and porous coating without any interstitial fibrous membrane.