Comparison of knee contact force between subjects with varying osteoarthritis severities

Osteoarthritis (OA) is the most common form of arthritis, with the knee being the most affected joint. A combination of biochemical, biomechanical (such as joint loading), and neuromuscular factors are thought to lead to the development and progression of OA. Gait analysis experiments have provided significant information about the biomechanical changes in OA. However, gait analysis alone cannot provide information about forces being produced by the muscles during dynamic activity.;Recent advancements in musculoskeletal modeling have enabled researchers to explore neuromuscular function (i.e. activation and muscle forces) during dynamic activity. In using musculoskeletal models, researchers can calculate muscle forces, and subsequently joint contact forces, providing insight into joint loading and the progression of such diseases as osteoarthritis.;This thesis first verified the use of the model and cost function available in OpenSim for pathological, OA gait. The study also estimated the knee contact force (KCF) in patients with varying degrees of OA severity using muscle forces and joint reaction forces (JRF) derived from OpenSim. Specifically, differences in knee contact forces were examined in subjects with varying degrees of symmetric, bilateral OA. Differences in knee contact forces were also examined between the less severe and more severe knees of subjects with asymmetric, bilateral OA. Additionally, these contact forces were compared to knee contact forces from corresponding subjects with symmetric, bilateral OA.;The results of this study suggest that differences in loading exist between varying OA severities in subjects with symmetric OA grades. Similar initial peaks of the knee contact forces imply that reduction of peak knee contact force may not be a compensatory strategy for OA patients; however, duration of high magnitude loads may be reduced with OA progression. Decreased second peaks of the knee contact forces suggests that decreased walking speed may not be an effect of OA, but rather a compensatory mechanism to reduce knee contact forces.;Subjects with a healthy knee and a contralateral knee with moderate OA exhibit bilateral compensatory strategies similar to subjects with symmetric, bilateral moderate OA. Similar trends were also seen in subjects possessing a knee with moderate OA and a contralateral knee with severe OA. These subjects also loaded their moderate knee longer than the contralateral severe knee. These results suggest that there may be unique compensatory strategies between asymmetric and symmetric subjects, as well as between the asymmetric groups.;This thesis successfully applied OpenSim to study knee contact forces in a pathological population. The findings show that KCF decreases with increasing OA severity due to reduced muscle forces from decreased walking speed. Furthermore, unique compensatory strategies exist for different levels of OA. Musculoskeletal modeling can provide a means of non-invasively estimating joint loads, and can provide valuable insight into the development and progression of OA through the study of joint kinetics and neuromuscular function.