To examine the association between physical exercise and the risk of severe knee osteoarthritis requiring arthroplasty.
A case-control study was carried out in which the cases were men (n=55) and women aged 55-75 yr (n=226) receiving knee arthroplasty for primary osteoarthritis at the Kuopio University Hospital. Controls (n=524) were selected randomly from the population of Kuopio province. Lifetime physical exercise was assessed retrospectively. Cumulative exercise hours were calculated and divided into two classes by mean (low/high).
The risk of knee osteoarthritis requiring arthroplasty decreased with increasing cumulative hours of recreational physical exercise. After adjustment for age, body mass index, physical work stress, knee injury and smoking, the odds ratios (with 95% confidence intervals) of knee arthroplasty were 0.91 (0.31-2.63) in men with a low number of cumulative exercise hours and 0.35 (0.12-0.95) in those with a high number of cumulative exercise hours, with a history of no regular physical exercise as the reference. For the women, the corresponding odds ratios were 0.56 (0.3-0.93) and 0.56 (0.32-0.98).
Moderate recreational physical exercise is associated with a decrease in the risk of knee osteoarthritis.