OBJECTIVE: To provide a clinically-meaningful interpretation of improvements in WOMAC scores among OA patients. METHODS: Data were obtained from three 12-week randomized clinical trials among 3,369 OA flare patients. The Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), PtGA & PhGA were administered at baseline and week-12. WOMAC is a 24-item instrument which contains three domains: pain, stiffness, and physical functioning and a summary score. PtGA & PhGA were measured on the following 5-point scale: very good, good, fair, poor, or very poor. Change scores were computed by subtracting patient’s baseline from week-12 follow-up scores. Responsiveness was estimated as the mean change score corresponding to each level of PtGA or PhGA improvement. RESULTS: At week-12, the number of patients experiencing improvements in PtGA and PhGA were: 1108 & 1,158 for one-level, 708 & 745 for two-levels, and 368 & 311 for three or more levels. The average improvement of WOMAC domain and total scores among patients experiencing one, two, or three or more levels of PtGA improvement were 2.3, 4.4, 6.5 for pain, 1.0, 1.7, 2.5 for stiffness, 7.3, 13.9, 20.4 for physical-functioning, and 10.1, 18.7, 27.4 for total WOMAC score. A similar responsiveness was found between average WOMAC scores and PhGA improvement, which were 2.3, 4.4, 6.6 for pain, 1.0, 1.7, 2.5 for stiffness, 7.5, 13.6, 21.0 for physical-functioning, and 10.3, 18.6, 27.9 for total WOMAC score. CONCLUSION: Using change scores responding to a one-level improvement of PtGA or PhGA or using the average difference of change between any two levels improvement of PtGA or PhGA, the clinically-meaningful improvement for WOMAC pain, stiffness, physical-functioning, and total WOMAC scores were approximately 2, 1, 7, and 10 respectively.