111 adult patients undergoing unilateral total knee arthroplasty were randomly assigned to periarticular injection or epidural analgesia for postoperative pain management. The purpose of this study was to compare the efficacy of each pain management technique in terms of pain relief and the frequency of opioid-related adverse effects. Results indicated a significant reduction in VAS pain scores at rest throughout the 72 hour follow-up period and earlier knee flexion motion in patients in the periarticular injection group compared with the epidural analgesia group. Patients in the epidural analgesia group had significantly higher incidences of nausea, but transient peroneal nerve palsy occurred frequently in patients in the periarticular injection group.