The long-term complications related to the patella were retrospectively evaluated for 891 knees (684 patients) that had had a total arthroplasty, with or without resurfacing of the patella, with use of an unconstrained, condylar, posterior-cruciate-preserving prosthesis. The study population comprised two groups of patients who were similar in size, age, sex distribution, and diagnosis. One group (396 knees [303 patients]) had had a total knee arthroplasty with patellar resurfacing and the other group (495 knees [381 patients]) had had the same procedure without resurfacing. The average duration of follow-up was six and one-half years (range, two to fifteen years). The decision to resurface the patella was based on subjective inspection of the articular surface and on assessment of patellar tracking at the time of the operation. Resurfacing was performed if there was loss of cartilage, exposed bone, gross surface irregularities, or tracking abnormalities. Complications occurred an average of three years (range, immediately postoperatively to nine years) after the operation in the group that had had resurfacing and an average of four years (range, immediately post-operatively to ten years) postoperatively in the group that had not had resurfacing. In the group that had had resurfacing, there was loosening of the patellar component in five knees, patellar subluxation in four knees, fracture of the patella in three knees, rupture of the patellar tendon in three knees, and chronic peripatellar pain in one knee. In the group that had not had resurfacing, the complications included patellar subluxation in five knees, rupture of the patellar tendon in two knees, and chronic peripatellar pain in fifty-one knees.(ABSTRACT TRUNCATED AT 250 WORDS)