We have studied 241 total condylar knee arthroplasties with replacement of the articular surface of the patella in 206 patients. The average age was 65 years. The technique of replacement of the patellofemoral joint emphasises realignment of the quadriceps mechanism, minimal excision of the patella to preserve subchondral bone, preservation of soft tissue attachments including the infrapatellar fat pad, and closure of the quadriceps without tension. The results of replacement have been good to excellent in 95 per cent of patients followed for two years or more. There were no subluxations, dislocations or fractures. Loosening was noted in one case associated with anterior knee pain. Discomfort was also noted with eccentric placement of the prosthesis where bone was left uncovered. We consider that routine replacement of the patello-femoral joint is advisable with total condylar knee arthroplasty.