Effects of functional knee bracing on muscle-firing patterns about the chronic anterior cruciate ligament-deficient knee.

Abstract

To examine the effects of functional knee bracing on the muscle-firing patterns about the chronic anterior cruciate ligament (ACL)-deficient knee in successful brace users. Cross-sectional comparative clinical trial. Motion analysis laboratory. Ten active individuals with unilateral, isolated, chronic (>18mo postinjury), ACL-deficient knees who subjectively reported improved function with a functional knee bracing. Each subject completed 3 single-leg hop maneuvers on their ACL-deficient knee with and without their knee brace while surface electromyographic activity was recorded from the quadriceps, hamstring, and gastrocnemius muscles. Muscle onset latency. Brace use significantly delayed the average onset of vastus lateralis activation before landing (123+/-47ms vs 109+/-30ms, P<.001), though significant interindividual variations existed. Bracing significantly altered the onset latency in 1 or more muscles in 9 of 10 subjects. In 4 subjects, a favorable change in the firing pattern was seen, whereas only 1 subject exhibited an unfavorable change. Without bracing, 5 of the 10 subjects fired the hamstrings or gastrocnemius muscles first; with bracing, 7 of 10 fired these muscles first. Brace use in this population did not consistently result in more favorable muscle firing patterns during the single-leg hop maneuver. Interindividual responses to brace use indicate the need for further research to investigate the multiple strategies that may exist to stabilize the ACL-deficient knee. In the meantime, functional knee brace use among ACL-deficient patients remains empirical.