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Lifetime physical activity and osteoarthritis Ratzlaff, Charles R


Introduction: The overall goal of this thesis is to improve understanding of physical activity (PA), one of the most important, modifiable but controversial risk factors in osteoarthritis (OA). OA is the major public health problem in musculoskeletal medicine and leading cause of physical disability in older adults. The ultimate purpose is to provide evidence to inform OA prevention strategies, something not currently available. Objectives: 1) To construct and describe lifetime trajectories of hip and knee joint force from physical activity in a large Canadian sample; 2) To validate self-report measures of medically-diagnosed OA and novel measures of joint vulnerability against clinical criteria; 3) To evaluate the relationship of lifetime joint force and hip and knee OA. Methods: PA data were collected online from 4,269 subjects via a validated PA survey in a national population-based cohort from 2005 to 2007 and subjects ranked and lifetime trajectories plotted in terms of the ‘cumulative peak force index’, a novel joint force measure. Validation studies were conducted in a sub-sample. Population-based multivariable studies examining the relationship between joint force and incident hip and prevalent knee OA were conducted. Results: 1) Overall women had slightly higher lifetime PA-related force then men. Six percent of subjects developed hip OA and seven percent knee OA during follow up. There was no risk from sport/recreational activity. Very high levels of total lifetime force (hip and knee), occupational force in men (knee) and household-related force in women (knee) were associated with an approximate 2-fold increase in risk of OA, as was previous joint injury (5-fold increase hip, 3-fold knee). At the knee, lower limb malalignment but not joint hypermobility, was associated with knee OA. Higher coordination was protective. Conclusions: Taken collectively, the results show that lifelong physical activity-related joint force is generally safe for the hip and knee, and the promotion of exercise as a major public health initiative should continue without concern for increased rates of OA. Very high levels of occupational force in men and household force in women were risk factors for knee OA. Joint injury, lower limb malalignment and lower coordination were associated with OA.

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