Short-term effects of a dedicated knee orthosis on knee adduction moment, pain, and function in patients with osteoarthritis

OBJECTIVE: To analyze knee joint loading, subjective pain relief, and improvements in function in patients with osteoarthritis (OA) with the use of 2 orthosis adjustments.

DESIGN: Patients were tested under 3 different conditions (without orthosis, orthosis at 4° valgus, and a neutral very flexible adjustment) in a crossover trial.

SETTING: University gait analysis laboratory with 3-dimensional motion analysis and force platforms.

PARTICIPANTS: Patients (N=11) with a clinical and radiographic diagnosis of unilateral OA in the medial knee compartment.

INTERVENTIONS: Patients wore a knee orthosis designed to unload the medial knee compartment for 4 weeks in 2 different adjustments (2 weeks in each adjustment).

MAIN OUTCOME MEASURES: Net knee adduction moment and net knee adduction angular impulse during the stance phase were analyzed by using inverse dynamics. Subjective pain relief, stiffness, and function improvement were evaluated using a questionnaire (Western Ontario and McMaster Universities Osteoarthritis Index). A 6-minute walk test and stair-climbing test also were performed.

RESULTS: Both orthosis adjustments induced subjective pain relief and improvement in function compared with the condition without orthosis. Knee adduction moment was significantly decreased with both adjustments, whereas the decrease observed with the 4° valgus adjustment was significantly greater than the flexible adjustment (25% vs 12.5%). Compared with the condition without orthosis, changes in knee adduction angular impulse of 29% and 15% were found with 4° valgus and the neutral flexible orthosis, respectively. Time required for the stair-climbing activity was significantly decreased using the orthosis in 4° valgus adjustment compared with the condition without orthosis. No significant differences were observed among conditions during the 6-minute walk test.

CONCLUSIONS: Both orthosis adjustments were effective in decreasing symptoms; however, a decrease in knee loading was more effective using the 4° valgus adjustment, which could contribute to avoidance of disease progression.