A noncemented and clinically stable porous-coated patellar component (PCA) 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.