The study objective was to quantify the association between daily physical activity measured by accelerometer and 1-year changes in symptoms among people with knee osteoarthritis.
Methods
Participants from the Osteoarthritis Initiative had knee radiographs and physical activity assessed using GT1M ActiGraph (Pensacola, FL) uniaxial accelerometers at the 48-month visit. Physical activity was calculated and categorized as tertiles of average daily minutes in light and moderate-to-vigorous activity. Outcomes were 1-year change in symptoms measured by Western Ontario and McMaster Universities scales, including pain, stiffness, and physical function. Adjusted multivariable linear models estimated the relationship between tertiles of light or moderate-to-vigorous physical activity and changes in knee symptoms.
Results
Among 1059 participants (55% were women; mean age, 66 ± 9 years), greater time in light activity was associated with a trend toward declined physical function (P = .01). Greater time in daily moderate-to-vigorous activity also was associated with declined physical function (P = .01) and increased pain (P = .08). None of these average changes in symptoms reached minimally important clinical differences. However, greater daily time in both activities was associated with a higher probability of worsening symptoms among persons with Kellgren–Lawrence grade 4 osteoarthritis.
Conclusions
Objectively measured daily activity was not associated with 1-year symptom improvements among community-dwelling adults with knee osteoarthritis. In those with advanced disease (Kellgren–Lawrence grade 4), greater daily minutes in physical activity were associated with worsening symptoms. How best to implement exercise regimens in persons with advanced knee osteoarthritis to reduce the deleterious impact on symptoms needs to be explored.
Knee osteoarthritis is a leading cause of pain and functional limitations among older adults. Although no effective remedy for osteoarthritis exists, the American College of Rheumatology and the US federal government recommend self-management strategies, such as regular physical activity. The beneficial effects of physical activity among patients with osteoarthritis generally are supported through randomized clinical trials. These trials vary in duration, intensity, and type of interventions; have selective populations, such as those with milder conditions who received intense encouragement and monitoring; and assess outcomes over short periods of time, all of which reduce generalizability to activities of normal daily living.
The details related to different levels of intensity, type, and duration for daily physical activity needed to improve symptoms and function among osteoarthritis populations are limited and contradictory. Nonexperimental studies examining the association between physical activity and symptoms have been cross-sectional or have used self-reported questionnaires to quantify activity. Longitudinal studies to quantify the impact of varying levels of intensity with regard to activities of daily living on pain, stiffness, and function in patients with knee osteoarthritis using objectively measured physical activity are needed to understand what intensity of activities should be recommended in what types of patients with osteoarthritis to improve symptoms.
The Osteoarthritis Initiative (OAI) data provide an opportunity to investigate the association between physical activity on 1-year changes in symptoms because they offer a subcohort with objectively measured physical activity and comprehensive examinations of knee symptoms. The current study will quantify the association of objectively measured physical activity of daily living on changes in symptoms in persons with knee osteoarthritis and evaluate the extent to which the observed association is similar across levels of disease severity. We hypothesized (1) that greater daily minutes of physical activity at baseline would be associated with improved symptoms over a 1-year period among patients with knee osteoarthritis and (2) that beneficial effects may not be observed across all levels of disease severity.
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-Shao-Hsien Liu, MPH, Jeffrey B. Driban, PhD, Charles B. Eaton, MD, Timothy E. McAlindon, MD, Leslie R. Harrold, MD, Kate L. Lapane, PhD
This article originally appeared in the May 2016 issue of The American Journal of Medicine.
