The American College of Rheumatology6 and other groups have developed criteria for diagnosing OA in the knee, hip, and hand; however, diagnosis is challenged by the limitations of X-ray findings in the early stages of OA and the fact that such findings do not correlate well with clinical symptoms. For example, estimates of the prevalence of knee OA vary widely according to whether clinical or radiographic criteria are used and the characteristics of the cohort studied.3, 5Computed tomography and magnetic resonance imaging can more readily detect cartilage and bony changes, but criteria for defining OA using them have not yet been established.