Simultaneous bilateral total knee arthroplasty was performed in twenty-six patients who had rheumatoid arthritis, and a patellar replacement was performed concurrently in one randomly selected knee in each patient. A lateral retinacular release was performed in all knees. The patients were followed for at least six years (mean, 6.6 years; range, 6.0 to 7.5 years), and the postoperative status of the patients was evaluated with the knee score of The Hospital for Special Surgery. Pain on standing and on ascending or descending stairs as well as tenderness of the patellofemoral joint also were assessed. The over-all score and the individual scores for pain, function, range of motion, muscle strength, flexion contracture, and instability were not significantly different between the knees that had had a patellar replacement and those that had not. However, pain on standing and on ascending or descending stairs as well as tenderness of the patellofemoral joint were only noted in knees that had not had a patellar replacement. These findings suggest that, in order to diminish pain on standing and on using stairs, replacement of the patella during total knee arthroplasty is preferable for patients who have rheumatoid arthritis.