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Osteoarthritis: Is it really caused by wear and tear?

Many of you have been told by different doctors that you have arthritis (more properly called osteoarthritis) due to a lifetime of wear and tear causing degeneration to the spine or other joints. A fascinating article was published in the British Journal of Sports Medicine entitled "Muscle dysfunction versus wear and tear as a cause of exercise related osteoarthritis: an epidemiological update" [2004;38 (5):526-535]. The author looked at what is called primary osteoarthritis, i.e., arthritis not due to genetic disease, fractures, bone deformities, or any of the rheumatoid types of arthritis. The study was limited to the knee and hip. The question the author asked was whether "exercise related osteoarthritis" was due to "wear and tear" or muscle dysfunction.

The muscle dysfunction theory says that contracting muscles are the main force absorbers of the joints and since regular exercise improves muscle function (strength and flexibility), exercise would not increase the incidence or worsen osteoarthritis. Previous studies have shown that strengthening exercise has helped patients with mild or moderate osteoarthritis and that tired muscles allow greater forces to the joints. The theory concludes that the bone spurs seen on X-rays of arthritic joints may be the body's attempt to increase the stability of the joint to make up for the poorly functioning (weak and inflexible) muscles.

If the "wear and tear" theory is true, exercise should worsen the arthritis. For example, the greater the distance someone runs the worse the wear and tear on the joints. According to the literature, recreational running and soccer did not increase the risk of osteoarthritis. Even subjects older than 50 were not affected by the amount of mileage they ran. There was, however, increased osteoarthritis in elite athletes. This makes sense because elite athletes typically push their bodies to the limit and play with injuries, both of which cause muscle dysfunction.

The author hypothesizes that when muscles are unable to contract adequately due to age, fatigue, lack of use, or prior injury more force is transmitted to the bones of the joint causing the arthritic changes. Even more interesting and pertinent, if there is muscle dysfunction one area, say the thigh, the arthritis might not necessarily occur in the joint adjacent (hip) to the injured muscle. Knee injuries may be the cause of hip arthritis and vice versa, since the muscles of the thigh should absorb the forces across both joints. Even when discussing the relationship of obesity to arthritis, muscle dysfunction rather than wear and tear may make more sense. Increased body weight requires the muscles to attempt to absorb more force. If the obese person is not fit (has a loss of strength, flexibility and endurance in his/her muscles) then the greater the bodyweight the more the stress at each weight-bearing joint (lower back, hips, knees, ankles).

The bottom line is (and I think you may have heard this from me before) a regularly performed exercise program (with the right exercises and correct exercise technique) may not only help arthritic patients, but may be the best way to prevent arthritis in the first place. WHAT A THOUGHT!