Objective: To compare objectively measured physical activity in older adults with symptomatic knee osteoarthritis (OA) with similarly aged adults without osteoarthritis (OA) or knee symptoms from the general population. Methods: We included people ages 50–85 years with symptomatic knee OA from the Osteoarthritis Initiative (OAI, n = 491), and ages 50–85 years from the general population using National Health and Nutrition Examination Survey (NHANES, n = 449) data. A uniaxial accelerometer was worn for ≥10 hours/day for ≥4 days in the NHANES group in 2003–2004 and in the OAI group in 2008–2010. We calculated time spent in moderate-to-vigorous physical activity (MVPA in minutes/day) and described differences in MVPA and demographic variables between the samples. We conducted matched-pairs sensitivity analyses to further evaluate the role of potential confounders. Results: Both cohorts had similarly low levels of physical activity in age- and sex-specific strata. Time in MVPA ranged from a median of 1–22 minutes/day in people with symptomatic knee OA, and from 1–24 minutes/day in the general population without OA or knee pain. These results were similar in sensitivity analyses. Conclusion: Time spent in MVPA was similarly low in those with symptomatic knee OA as in older adults without knee pain or OA.
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