The effect of extension constraint knee bracing on dynamic balance, gait mechanics, and joint alignment.

Abstract

To examine how an extension constraint knee brace affects active and passive standing knee joint alignment, dynamic balance, and gait mechanics. Repeated-measures, within-subjects design. Research laboratory. Persons (N = 24) with no current diagnosed gait dysfunction or neuromuscular limitations that limit activities of daily living. All subjects were tested with use of dynamic balance and gait analysis. Dynamic balance was examined with the Lower Quarter Y Balance Test. Gait analysis was conducted at a freely chosen walking speed for 2 conditions: (1) use of a brace with free range of motion (FROM) and (2) use of a brace with 30-degree extension constraint (ECON). In a subset of subjects, radiographs were used to examine standing knee alignment for 3 conditions: (1) FROM, (2) use of a knee ECON brace in a relaxed position; and (3) use of a knee ECON brace with maximal volitional quadriceps contraction. Peak knee flexion, knee flexion range of motion, peak vertical ground reaction force during weight acceptance and propulsion, and maximum reach distance in the anterior, posteromedial, and posterolateral directions were measured. Differences in dynamic balance were observed between ECON and FROM for the anterior reach. Peak knee flexion increased 3.2° and peak knee extension decreased 7.4° in the ECON condition. Vertical GRF values were found to increase bilaterally during ECON at midstance but decreased bilaterally during propulsion. Radiographic images revealed that the ECON elicited a 22.2° flexion contracture with minimal quadriceps activation but only reduced motion by 4.8° with maximal volitional quadriceps activation. Extension constraint knee braces alter joint alignment, dynamic balance, knee mechanics during gait, and vertical loading during gait. However, the changes in motion observed were lower than those induced by the constraining mechanism.