Effect of Physical Activity on the Development of Knee Osteoarthritis
Felson DT, Niu J, Clancy M, Sack B, Aliabadi P, Zhang Y. Effect of recreational physical activities on the development of knee osteoarthritis in older adults of different weights: The Framingham Study. Arthritis Rheum (Arthritis Care Res) 2007;57: .
What problem was studied?
Regular physical activity is recommended for all people. However, how exercise affects the development of osteoarthritis (OA) is uncertain. One school of thought is that frequent load-bearing exercise causes cartilage to become thicker, thereby preventing knee OA. Another school of thought is that the repetitive motions associated with physical activity, particularly in overweight individuals, may contribute to the “wear and tear” component of knee OA. David Felson, MD, and his team from Boston University School of Medicine and Brigham and Women’s Hospital in Boston performed a longitudinal, prospective study examining the effect of recreational physical activity on the development of knee OA in people at risk for OA, many of whom were overweight or obese. Although this particular study was funded by the National Institutes of Health and Boston University, Dr. Felson has received two research grants from the Arthritis Foundation, one to study bone density and another to study the effects of vitamin K on OA.
What was done in the study?
Members of the Framingham Offspring study were recruited as part of a study of the inheritance of OA. Of the subjects, 1,279 were included in an evaluation of physical activity and OA development. The participants answered a questionnaire about physical activity, had knee X-rays taken and answered questions about knee symptoms. They then had the same evaluation approximately nine years later. The participants included older individuals (mean age, 53.2 years), many of whom were overweight (mean body mass index, 27.4), allowing the scientists to evaluate the effects of activity on OA development and to test whether weight had any influence on the results.
What were the study results?
Of the 2,259 knees evaluated at the end of nine years, 222 (9.8%) had narrowing of joint space evident in the X-rays, 215 (9.5%) developed OA apparent by X-ray and 173 (7.2%) had knee symptoms (pain and stiffness). Walking for exercise was the most commonly mentioned physical activity among the participants, and none of the measured parameters were affected by walking -- risk of developing OA was neither increased nor decreased by walking for exercise. Likewise, those exercising at a more vigorous intensity (enough to work up a sweat) had no greater risk of developing OA than participants who did not exercise.
When analyzing the data separated by sex and body mass index, the results were the same. Those whose BMI was above the median of the group and who performed regular physical activity had no greater risk of developing knee OA than those whose BMI was below the median and engaged in regular exercise.
What is the relevance to people at risk of developing OA?
Patience White, MD, Chief Public Health Officer of the Arthritis Foundation pulls together the significance of this research. “The finding of Dr. Felson’s study of middle aged and elderly peoples’ physical activity levels and their risk of OA is welcome news for people who are at risk for developing osteoarthritis, the most common form of arthritis in the US, affecting 27 million Americans and resulting in significant joint pain and disability. This study reassures them that moderate to high intensity recreational physical activity with its many health benefits will not result in increasing their risk of developing painful osteoarthritis. Now middle-aged and older Americans at risk for osteoarthritis can act to improve their health by consulting their physician about following the Centers for Disease Control and Prevention recommendations to undertake 30 minutes of physical activity of at least moderate intensity most days of the week.”
