The supplements glucosamine and chondroitin have been put to the test in several studies for their ability to relieve pain and possibly preserve cartilage in people with osteoarthritis. Knee pain is a common complaint in people over age 40. To diagnose the cause, physicians may use imaging techniques, such as magnetic resonance imaging (MRI) and weight-bearing X-rays. A program of physical therapy is standard after joint replacement surgery to facilitate the return to normal physical function. Biologic drugs are standard treatment for many people with rheumatoid arthritis. Because these drugs are derived from living cells, it has not been possible to create traditional generic versions of them, even after the patents have run out.