UNDERSTANDING SELF-REPORTED INSTABILITY USING GAIT OUTCOMES AND WALKWAY SURFACE TRANSLATIONS IN THOSE WITH KNEE OSTEOARTHRITIS
Baker, Matthew Douglas
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Knee osteoarthritis (OA) is a progressive disease that is highlighted by debilitating symptoms that have detrimental impacts on physical activity. One such symptom is knee instability, which is self-reported in 60-80% of the OA population and 30-60% reported instability impacts activity. Self-reported instability, or sensations of buckling, shifting or giving way have been linked to poor knee joint confidence and walking difficulties. The objective of this thesis was to understand the inter-relationships that exist between knee function during gait, self-reported instability, and responses to direct and indirect walking perturbations in asymptomatic individuals and people with knee OA. Three related objectives were conducted. For objective one, asymptomatic participants and individuals with moderate knee OA, subclassified as OA Stable and Unstable were tested in the JAR lab. Knee motion, moments and muscle activation patterns collected during treadmill walking were analyzed. Significant muscle activation magnitudes and patterns were found, identifying unique activation patterns to the OA unstable group compared to OA stable and asymptomatic groups. For the second objective, an asymptomatic group and individuals with moderate knee OA experienced unexpected direct and indirect, medial 3cm frontal plane walk surface translations of the symptomatic and asymptomatic limbs during gait. Groups responded with elevated and prolonged muscle activation patterns and no significant change in sagittal and frontal plane motion and moments. For the final objective, a preliminary analysis was completed on direct and indirect perturbation responses in an asymptomatic group, and individuals with moderate OA dichotomized into OA stable and OA unstable groups. All groups maintained joint motion and moment ranges, using elevated and prolonged muscle activation magnitudes and patterns. These studies show that individuals who self-report instability walk with activation patterns that provide increased knee joint active stiffness. Furthermore, responses to direct and indirect perturbations in asymptomatic, moderate OA groups, and moderate OA groups dichotomized by self-reported stability increase and prolong muscle activation magnitudes patterns to provide active stiffness to maintain knee function. Responses to indirect and direct perturbations are in the direction that those with moderate OA and instability walk with day-to-day and provides information into the pathomechanics used to maintain knee function.