BACKGROUND: Epidural opioids and local anesthetics provide excellent postoperative analgesia. In addition, soft tissue and intra-articular injection of bupivacaine and morphine may have a beneficial analgesic effects after total knee arthroplasty (TKA). This study was designed to assess the additional analgesic effect of combined soft tissue, and intra-articular injection of morphine and bupivacaine in patients undergoing TKA under spinal anesthesia with continuous epidural morphine and bupivacaine injection. METHODS: Forty patients aged 55 to 75 years for a TKA under spinal anesthesia were randomly divided into 2 groups. The both group of patients received a continuous epidural infusion using a two-day infusor containing morphine 5 mg in 100 ml of 0.125% bupivacaine. The experimental group of patients (n = 20) received soft tissue, and intra-articular injection containing 10 mg morphine in 100 ml bupivacaine 0.125%. The control group of patients (n = 20) received soft tissue, and intra-articular injection of 100 ml normal saline. Postoperative pain was assessed using the visual analog scale (VAS) at 1, 2, 4, 8, 12, 24, and 48 h postoperatively and side effects, such as hypotension, nausea, vomiting, pruritus, and respiratory distress were recorded. Whenever patients demanded supplemental analgesia, diclofenac sodium 75 mg was injected intramuscularly and the need for additional analgesic requirement was recorded. RESULTS: The experimental group of patients had significantly lower pain score and analgesic requirements than the control group for 2 days. There was no difference in the incidence of side effects between groups. CONCLUSIONS: Combined soft tissue, and intra-articular injection of morphine and bupivacaine with continuous epidural morphine and bupivacaine infusion reduces postoperative pain and supplementary analgesic requirements than continuous epidural morphine and bupivacaine infusion only in patients undergoing TKA.