The pain relief provided by intra-articular injection of morphine plus bupivacaine after total knee arthroplasty (TKA) plus partial synovectomy in patients with rheumatoid arthritis was compared with pain relief after TKA alone in patients with osteoarthritis. There were lower pain scores, a much smaller requirement for systemic analgesics, longer duration until the first requirement of systemic analgesics, and improvement in the range of motion of the knee joint in the patients who received intra-articular injection of analgesics. There was more pronounced postoperative analgesia in the patients with rheumatoid arthritis than in the patients with osteoarthritis in the study groups that received intra-articular injection of analgesics.