An orthopaedic surgical instrument includes a patella trial and drill guide (14) that may be used both to perform a surgical trial of the patello-femoral joint and to guide the surgeon in drilling a number of anchor holes in the patella of the patient. The instrument has a posterior trial bearing surface (52) configured to articulate with a condylar surface of a prosthetic femoral component, and comprising a curved peak surface. An anterior surface (62)has a number of outwardly extending spikes (64). Drill guide holes (76) extend through the instrument from the posterior trial bearing surface to the anterior surface, and an alignment bore (90) extends through the instrument from the posterior trial bearing surface to the anterior surface.
