Knee pain is a severely disabling condition that can affect daily living. One of the most common causes of knee pain is osteoarthritis (OA). This is a condition that affects over 27 million people in the U.S. OA is a “wear and tear” of the natural cushioning between the knee joint. Normally this cushioning provides support and acts as a shock absorber. However, as it is worn down, the result is bone rubbing on bone, which causes pain, swelling, and stiffness.