We compared the outcome of total knee arthroplasty in 19 patients who had had previous patellectomy with the results in a matched series of arthroplasties performed on knees in which the patella was intact. The mean follow-up was 63 months (21 to 114). In the study group, the outcome was poor in five patients. There was instability in the coronal plane in three patients and persistent pain in four. Three supracondylar fractures occurred. The overall complication rate was 36%. In the control group, pain was relieved in every case and there were no complications. Total knee arthroplasty has a higher complication rate and inferior results if the knee has undergone prior patellectomy.