Lifetime exercise is safe for your knees.

In the good news department, here's another study dispelling the myth that lifetime exercise "wears down" your knees causing future osteoarthritis. This study surveyed 4,316 people in England on their exercise habits, incidence of osteoarthritis, knee injury history, and body composition. The researchers concluded that normal lifetime exercise does not damage your knees or increase your risk of osteoarthritis in the long run, at least not directly. The only strong association with osteoarthritis was injury, and of course, runners do suffer injuries--as many as 75% of runners are injured each year.

While most running injuries are injuries to soft tissue that do not affect the integrity of the knee joint or increase the risk of future osteoarthritis, the important takehome lesson is to do everything you can to prevent injury in the first place. The risk of ultimately suffering chronic osteoarthritis pain and disability increases dramatically when your knees are injured. According to American Running Editorial Board Member Marvin Bloom, M.D., running on injured knees (such as a tom meniscus or a loss of articular cartilage) is like running a car engine without motor oil--you're asking for trouble. If your knees hurt and you don't fully recover with a day of rest, see a sports medicine professional and find out why it is hurting and what you can do about it (Annals of Rheumatic Diseases, 2001, Vol. 60, August, pp. 756-764)