Does exercise increase the risk of knee OA

Since CDC wants us to exercise, it's worth thinking about other risks. This paper is a random survey of England. Extracted conclusions were

From 4316 people originally interviewed, 216 eligible cases (66 men, 150 women) were identified (mean age 57.1). [about 5% of this random sample of England.] Each case was matched to four controls. When habitual sport/exercise participation were examined during a subject's life, only exposure to regular long walks and being physically active between the ages of 20 and 24 suggested any association with developing knee OA later in life. The only strong association found was a greatly increased risk of knee OA having previously sustained a knee injury (odds ratio 8.0)

The Dodger actually didn't read the full text with great enthusiasm. This was retrospective assessment, so the rate of OA is prevalence and not stratified by age. The Dodger remembers they collected BMI information, so they must have asked about smoking too, but reported no association with OA. There appeared to be no consideration of occupational activity, only physical fitness stuff. There's no data about activity during 40% of waking hours. Plus, the Dodger imagines that persons with physically demanding jobs may be less likely to play squash on their off hours, which would introduce negative confounding with risks of exercise.

Ann Rheum Dis. 2001 Aug;60(8):756-64.

A case-control study to investigate the relation between low and moderate levels of physical activity and osteoarthritis of the knee using data collected as part of the Allied Dunbar National Fitness Survey.

Sutton AJ, Muir KR, Mockett S, Fentem P.Department of Epidemiology and Public Health, University of Leicester, 22-28 Princess Road West, Leicester LE1 6TP, UK. ajs22@le.ac.uk