Evaluation of function in individuals with knee osteoarthritis

Sammanfattning: Introduction: Osteoarthritis, the most common joint disease, results in joint pain and limited function. In clinical practice, the array of measurements used to evaluate function are generally restricted to patient-reported outcome measures and performance-based tests, as they do not require special equipment. What these measures are unable to answer is how a given activity is performed. Thus, there may be additional important aspects of function, including examination of movement patterns, which could provide complementary information in the evaluation of function. This thesis evaluates methods used to objectively assess function – e.g., gait patterns, movement strategies, and performance-based function – in individuals with knee osteoarthritis. Methods: The studies include 40 individuals with primary knee osteoarthritis scheduled for total knee arthroplasty and a convenience sample of 25 healthy controls matched by age strata to individuals with osteoarthritis. All study participants completed a three-dimensional motion analysis session that rendered measurements of gait patterns and movement patterns used to perform a Sit-to-Stand test. Participants performed three performance-based tests including the Five Times Sit-to-Stand test, the Timed Up and Go test, and the Single Limb Mini Squat test. Participants completed one knee-specific questionnaire and one generic health-related quality of life questionnaire. Perceived pain was evaluated using a visual analogue scale. Individuals with osteoarthritis were evaluated within one month prior to total knee arthroplasty and one year after surgery. Controls were evaluated once. Results: In Study I, the overall gait pattern, as represented by the Gait Deviation Index for kinematics and kinetics, was found to be affected on both the painful osteoarthritis limb and the contralateral limb compared to controls. In Study II, one year after surgery, measures of overall gait patterns and performance-based function were found to be improved although not restored to the level of healthy controls. In Study III, individuals reporting improvement in Knee-related Quality of Life displayed improved knee biomechanics during gait, whereas patients reporting small or no improvement in Knee-related Quality of Life remained unchanged one year after surgery despite similar reductions in pain. In Study IV, the body’s Center of Mass was shown to be shifted anteriorly and towards the contralateral limb in individuals with osteoarthritis performing the Five Times Sit-to-Stand test. After surgery, when pain was substantially reduced, Center of Mass trajectories were comparable to those of healthy controls. Conclusions: Alterations in joint loading were associated with both performance-based function and patient-reported outcomes whereas kinematic gait alterations were not associated to either, indicating that clinical outcome measures of function are not aligned with kinematic gait deviations. Based on post-operative changes in Five Times Sit-to-Stand test performance, individuals with considerable gait pattern improvements were identified. However, patient-reported measures of function could not detect differences between individuals improving in performance-based function and those who did not. Nevertheless, improvements in knee flexion-extension range during gait were related to large improvements in Knee-related Quality of Life. The body’s Center of Mass trajectory during the Five Times Sit-to-Stand test was found to be a sensitive and responsive measure of functional compensations typical of knee osteoarthritis pathology.