Knee pain affects one in 10 US adults older than 65 years.1 The most common cause of knee pain in adults is osteoarthritis (OA); it has been estimated that one in four adults has knee OA.2-3 The physical manifestations of OA include joint space narrowing, cartilage hardening and thickening, tears or lesions in cartilage, and formation of osteophytes. Although OA is common, especially as one ages, the age at which one develops knee OA and the of severity symptoms, which include pain and stiffening, depend on a variety of etiological factors, s