A patella drill guide (14) and trial instrument includes a posterior trial bearing surface (52) configured to articulate with a condylar surface (154) of a prosthetic femoral component. The posterior trial bearing surface has a curved peak surface that defines the posterior-most surface of the patella drill guide and trial instrument. The opposite anterior surface (62) has a number of spikes (64) extending outwardly therefrom. Drill guide holes (76) extend through the patella drill guide and trial instrument from the posterior trial bearing surface to the anterior surface.
