Effect of Common Gait Modifications on Knee Joint Loading and Loading Environment in Persons With Knee Osteoarthritis

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URL: http://udspace.udel.edu/handle/19716/17434

Abstract

Knee osteoarthritis (OA) is a leading cause of disability in older Americans affecting 12 percent of people greater than 60 years of age with these persons primarily complaining of knee pain and instability. Eighty percent of persons with painful OA report a limitation in functional mobility including 25 percent reporting they cannot perform a major activity of daily living (ADL). Walking is an important ADL frequently limited in this population and as such is frequently investigated with changes in preferred walking speed and knee kinematics being identified. The effectiveness, or lack thereof, of these gait modifications on joint loading is not currently well understood and was investigated in this dissertation. In Aim 1, we examined the effect of walking speed on cumulative joint loading after accounting for the distance traveled within the gait cycle and found that the reduced walking speed frequently exhibited by persons with knee OA is likely not an effective strategy to reduce cumulative joint loading. Furthermore, if these subjects were to increase their self-selected walking speeds to match that of their healthy older adult counterparts, a 2.7-10.4% reduction in cumulative joint loading would be possible. In Aim 2, we investigated the effect of the altered sagittal knee kinematics on the peak joint contact force (JCF) and identified that the reduced late stance knee extension exhibited by persons with knee OA was associated with a decrease in 2nd peak JCF; however the increased early stance knee flexion exhibited by these subjects was associated with an increase in the 1st peak JCF. The 2nd peak JCF was found to be of significantly greater magnitude than the 1st peak, suggesting the altered sagittal knee kinematics observed by the population may be an effective strategy to reduce the magnitude of joint loading during gait. In addition to the duration and magnitude of joint loading, the area of loading distribution significantly influences the contact stresses experienced within the joint. The articular cartilage contact area has previously been found to be a valid surrogate for the area of loading distribution and we identified that accounting for the anthropometric variation in this measure before evaluating changes with the development of OA is an important consideration (Aim 3). Kinematic (Aim 4a) and kinetic changes (Aims 4b,c) that resulted in an increase in joint loading were associated with a corresponding increase in the area of loading distribution in healthy older adults, but not in subjects with knee OA suggesting that in addition to the elevated joint loading frequently observed in this population, the joint loading environment may also be altered. The results of these studies should be used as the basis for longitudinal studies to identify those at risk of developing knee OA and those with established OA with the long term goal of developing rehabilitation strategies to minimize the effect of the disease on ADLs.

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