This study compares the responsiveness and relative effect sizes of the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) with the Medical Outcomes Study Short Form Health Survey (SF-36) in a randomized clinical trial for treatment of osteoarthritis (OA).
Patients with OA of the knee or hip were randomized to receive either placebo or 2,400 mg/day of ibuprofen for 28 days. Patients completed the WOMAC and SF-36 at baseline and days 7, 14, and 28 of the trial.
Patients receiving ibuprofen showed significant improvement in WOMAC pain, physical functioning, and the total score, while improvement was detected only for bodily pain on the SF-36. The WOMAC detected significant differences between ibuprofen and placebo for pain and physical functioning, whereas the SF-36 detected differences for the bodily pain subscale.
These results suggest the WOMAC has greater power to detect treatment differences than the SF-36, with respect to pain and physical functioning, in OA clinical trials.