Given once daily, extended-release (ER) tramadol HCl (ULTRAM^® ER) reduces pain and related symptoms of osteoarthritis (OA). Two 12-week, double-blind, placebo-controlled, randomized, parallel-group studies were conducted to compare the analgesic efficacy, safety, and tolerability of tramadol ER (100, 200, 300, and 400 mg for Study A and 100, 200, and 300 mg for Study B) as compared to placebo in patients (20-80 years) with moderate-to-severe pain due to radiographically-confirmed OA of the knee or hip (Study A, N=1020; Study B, N=1011). This post-hoc analysis evaluated tramadol ER in patients ≥65 years (n=556) from both studies. Patients rated their arthritis pain utilizing a 100-mm (0=no pain, 100=extreme pain) visual analog scale (VAS); pain and related symptoms were assessed using the WOMAC OA index. Sleep effects were evaluated using the Chronic Pain Sleep Inventory scores based on a 100-mm VAS (0=never, 100=always). From baseline to Week 12, this analysis demonstrated: a significant improvement in the pain, physical function, and joint stiffness subscales of the WOMAC OA index and the composite score, and pain intensity VAS scores in the index and non-index joints for the tramadol ER 300-mg group (P ≤0.035 vs placebo); a significant decrease in awakening by pain at night and trouble falling asleep (100-, 200-, 300-mg groups); a significant decrease in awakening by pain in the morning (200- and 300-mg groups); and significantly better sleep quality (300-mg group; P <0.05 all parameters vs placebo). The most commonly reported adverse events for both studies were constipation, dizziness, nausea, headache, and somnolence. Based on the WOMAC OA Index scores and pain intensity VAS scores in this combined analysis of 2 studies, tramadol ER showed significant improvement in pain, stiffness, and functionality, and should be considered for the management of moderate-to-severe chronic pain associated with OA in elderly patients.