Strategies used during a challenging weighted walking task in healthy, older adults and subjects with knee osteoarthritis
Date
2010
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Publisher
University of Delaware
Abstract
Knee osteoarthritis (OA) is a degenerative joint disease that affects millions of people. While numerous gait differences have been identified between healthy adults and adults with knee OA and some studies have looked at how biomechanics differ during challenging conditions, none have studied healthy, older adults or adults with knee OA during a challenging weighted walking task. Because loading is important to the initiation and progression of knee OA and this type of challenging task will increase the forces that must be absorbed by the body, we investigated the effect of weighted walking on initial contact and loading response (weight acceptance task). We used a split belt instrumented treadmill and motion capture technology to analyze the gait of 40 subjects (20 healthy and 20 knee OA) walking at 1.0 meter per second while unweighted and weighted with 1/6th of their body weight in a front and back loaded weight vest. Subjects were grouped according to their Kellgren and Lawrence (K/L) radiographic score. Healthy subjects had a K/L ≤ 1, while knee OA subjects had a K/L ≥ 2. The analysis of initial contact focused on the position of the ankle, knee, and hip in the sagittal plane and step length. The analysis of the loading response included double support percent, peak braking force, peak hip flexion moment, peak knee flexion moment, knee flexion excursion and load rate. We used a two-way, x i repeated measures analysis of variance to check for differences within groups, within conditions, and interaction effects. We found significant differences for hip flexion angle at initial contact, double support percent, and load rate. Follow-up t-tests revealed subjects with knee OA had a larger double support percent and hip flexion angle at initial contact and a decreased load rate compared to unweighted, healthy, older adults. Also, both groups increased their double support percent in response to the challenging weighted walking task, but only the healthy, older adults increased their hip flexion angle at initial contact and decreased their load rate. Correlation and regression analysis of the significant findings found that unweighted, knee OA subjects had a significant relationship between the hip flexion angle at initial contact and double support that did not exist in the healthy, older adults and did not remain when they were weighted. The relationship between load rate and double support in the knee OA group got stronger during the weighted condition, but did not persist in the healthy, older subjects. It appears that during the weighted condition the knee OA group places priority on decreasing loads, secondarily increasing weight-bearing stability, while the healthy, older adults make weight-bearing stability a priority, secondarily decreasing load rate.