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Osteoarthritis, Exercise, and Knee Replacement

Regular, vigorous physical exercise confers numerous benefits. These include markedly postponing disability, prolonging life, strengthening bones, improving cardiac function and quality of life, reducing frailty, and retarding progression of aging markers in many organ systems1,2,3,4. Effects of exercise upon radiographic osteoarthritis (OA), particularly of the knee, have also been examined, partly because the original “wear and tear” hypothesis of OA development suggested that excessive weight-bearing exercise might cause accelerated joint damage and might result in more knee replacement surgery.

The “wear” component of this hypothesis has been generally disproven, although elements of the “tear” component remain in the context of contact sports5. Pain-free exercise does not appear to accelerate OA development, and has been postulated to have a protective effect. For example, after accounting for body mass index (BMI), the Framingham Study6,7,8 reported no association between exercise and knee OA. Rogers, et al 2 showed a protective effect of exercise for knee OA. Manninen, et al 9 found a dose-response protective exercise effect for knee arthroplasty, and Racunica, et al 10 showed an exercise benefit to knee articular structures during development. Similarly, Jones, et al 11 found healthier cartilage in exercising children. Recently, we observed a trend toward fewer knee arthroplasties in vigorous lifetime exercisers, principally long-distance runners over hard surfaces12. Epidemiologic studies of OA identify age, female gender, and obesity as major risk factors for knee OA, but they do not include exercise (absent trauma) as a risk factor1,13,14. Indeed, numerous reports describe exercise as currently perhaps the single most important treatment for OA.

Responding to issues related to … 

Address correspondence to Dr. Bruce; E-mail: bbruce{at}stanford.edu