Weight-bearing recreational activity was associated with a 22% increased odds of developing knee osteoarthritis (OA) in a large prospective cohort study in the Netherlands, but notably, the increased risk was seen only in those with low levels of lower-limb muscle mass.
The findings point toward the value of “tailored advice” for physical activity, and suggest that “caution is needed when engaging in weight-bearing activity, especially for individuals with low levels of lower-limb muscle mass,” Yahong Wu, MD, and coinvestigators, of the Erasmus Medical Center in Rotterdam, the Netherlands, wrote in JAMA Network Open.
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Investigators used data from sequential cohorts of the longitudinal Rotterdam Study, which enrolled people aged 45 and older starting in 1990. The 5003 participants in this new analysis of physical activity and knee OA had complete records of baseline recreational physical activity, baseline knee pain, and knee radiographs from both baseline and at least one follow-up exam. Those with radiographically defined knee OA at baseline were excluded.
The incident rate of radiographically defined (x-ray) knee OA among all participants was 8.4%, with a mean follow-up time of 6.33 years. Among 3492 individuals without baseline knee pain, the researchers found no increased odds of incident radiographic OA with non–weight-bearing activity (odds ratio [OR], 1.04; 95% CI, 0.95-1.15; P = .37) but a significant association of weight-bearing activity with OA incidence (OR, 1.22; 95% CI, 1.10-1.35; P < .001).
A stratification analysis of a subset of participants whose lower-limb mass had been measured by dual-energy x-ray absorptiometry (DXA) showed, however, that the association of weight-bearing activity with incident OA was limited to patients in the lowest third of lower-limb muscle mass index (LMI), who had a 53% increased likelihood of developing knee OA (OR, 1.53; 95% CI, 1.15-2.04; P = .003).
For patients in the middle and upper tertiles, there was no significant association between weight-bearing activity and the odds of incident OA (OR, 0.93; P = .73, and OR, 1.15; P = .40, respectively).
The findings are reassuring overall, said Kelli D. Allen, PhD, research professor of medicine and exercise physiologist at the University of North Carolina at Chapel Hill, who was asked to comment on the study. “The study corroborates prior research showing that for most people, weight-bearing recreational activity does not increase the risk of knee osteoarthritis. This should be encouraging for people who want to increase their physical activity,” she said.
Durham VA Medical Center
Dr. Kelli D. Allen
The study also suggests that “for people with low lower-limb muscle mass, there may be some considerations to make regarding the best type of physical activity to prevent future knee osteoarthritis,” she said in an e-mail. “The best approach may include non–weight-bearing activities, which could include biking, swimming, or other water exercises, along with strengthening exercises that help to increase muscle mass.”
Other studies, Dr. Allen said, have shown that low muscle mass itself is a risk factor for knee OA.