Combined Effects of Physical and Psychological Factors on Physical Activity in Adults with Osteoarthritis

This dissertation research aimed to (i) investigate the associations between muscle strength, gait mechanics, and physical function with physical activity in people with osteoarthritis (OA); and (ii) determine how fear of movement (kinesiophobia) contributes to explaining the variations in physical activity with these measures. Cross-sectional data from participants with self-reported doctor diagnosed uni-or bilateral OA of the knee were included. The following measures were collected and analyzed throughout this work. Physical activity, kinesiophobia, and pain were assessed by self-report using the University of California, Los Angeles activity rating scale, Tampa Scale for Kinesiophobia, and The Knee Injury and Osteoarthritis Outcome Score pain subscale, respectively. Isometric knee extensor and flexor muscle strength were measured using an isokinetic dynamometer. Gait parameters were collected with three-dimensional gait analysis while participants walked on an instrumented split-belt treadmill at a self-selected speed. Physical function was assessed using the following performance-based measures: four square step test, 30-sec chair stand test, timed up and go, 40-m fast paced walk, and habitual gait speed. Overall, the findings from the three investigations convey that greater knee strength, higher peak sagittal plane joint moments at the ankle and hip during walking gait, faster self-selected walking speed, and better performance-based physical function are all independently related to higher physical activity level in people with knee OA. The degree of kinesiophobia significantly contributes to explaining the variation in activity level even after accounting for these measures. A lower degree of self-reported kinesiophobia (or less fear of movement) was significantly associated with higher physical activity level across all three investigations. Assessing kinesiophobia in patient evaluations may help with identifying individuals that are more likely to avoid physical activities or adhere to exercises due to behavioral adaptations which have a global effect on the body.