Osteoarthritis (OA) is the leading cause of disability among adults. As the population ages, increased intervention efforts are vital to controlling the individual and public health toll of this chronic, crippling joint disease.

Along with early diagnosis, moderate exercise is one of the most effective ways to reduce pain and improve function in patients with OA of the knee and hip. Yet, more than 60 percent of U.S. adults with arthritis fail to meet the minimum recommendations for physical activity.

Based on the "wear and tear" nature of OA, the commonly held belief is that exercise will not strengthen joint cartilage and may even aggravate cartilage loss. Until recently, investigators were unable to put that belief to the test. Radiographs, the standard measure of OA's progression, made it impossible to assess cartilage before severe cartilage damage had occurred. Advances in magnetic resonance imaging (MRI) now make it possible to study cartilage changes earlier in the course of OA.

Two researchers in Sweden, Leif Dahlberg, M.D., Ph.D., and Ewa M. Roos, P.T., Ph.D., used a novel MRI technique to determine the impact of moderate exercise on the knee cartilage of subjects at high risk for developing OA-middle-aged men and women with a history of surgery for a degenerative meniscus tear.

In the November 2005 issue of Arthritis & Rheumatism (http://www.interscience.wiley.com/journal/arthritis), they share evidence to support the therapeutic value of exercise for OA patients, for improving not only joint symptoms and function, but also the quality of knee cartilage.