A knee prosthesis assembly can comprise a patella prosthesis adapted to be secured to a natural patella portion having an anterior surface and a posterior surface. An articulating portion can have a posteriorly facing portion and an anteriorly facing portion. The posteriorly facing portion can have a spherical articular surface. A porous portion can have a first portion that engages the anteriorly facing portion and a second portion that engages the natural patella portion. A fastener can pass entirely through a passage formed at a centermost portion of the natural patella portion from the anterior surface to the posterior surface and into a bore defined in the centermost portion of the porous portion to securably engage the porous portion.
