2. Could PEMF cause repair of microfractures in trabeculae underlying the joint, stopping production of pain from these structures? PEMF were first introduced into clinical medicine as treatment for unhealed fractures, and are also used to promote healing or ordinary fractures. They have also been shown to cause thickening of bone in circumstances in which bone loss (osteoporosis) has occurred. Treatment of patients with osteoarthritis might increase formation of bone at sites where it is needed, causing painful microfractures to heal and make the subarticular bone denser and better able to withstand physical stress without causing pain.

3. Could the PEMF affect the forces leading to osteophyte formation? When osteophytes (outgrowths of cartilage and bone at the joint margins seen in osteoarthritic joints) are forming, they are often the site of considerable pain and on physical examination of the joint, the site of swelling, warmth and tenderness. The mechanism responsible for osteophyte formation is not yet known, but given the knowledge of the role of electrical signals in causing bone formation, alterations in the patterns of such signals by the articular cartilage breakdown is a possible basis. Since PEMF alter the electrical signals in joints, they could affect the process of osteophyte formation. Turning off osteophyte formation could stop pain and account for the decreased tenderness seen in treated patients.

4. Could PEMF lead to collagen production in other joint structures, especially the capsule, strengthening it and making it better able to withstand abnormal physical stresses of an osteoarthritic joint during Joint use without generating pain signals?

These and other hypotheses have been suggested as possible mechanisms of action of PEMF They can serve as the basis for design of further studies. Based on the convincing clinical evidence of efficacy we feel that such studies will be worthwhile and will eventually lead to knowledge of the mechanism of action and answer such vital questions as whether PEMF can alter the progression of the basic disease processes occurring in osteoarthritis.