Immediate Effects of a Brace on Gait Biomechanics for Predominant Lateral Knee Osteoarthritis and Valgus Malalignment After Anterior Cruciate Ligament Reconstruction

Background: Lateral knee osteoarthritis is notably common after anterior cruciate ligament reconstruction (ACLR). While valgus bracing has been investigated as an intervention for medial knee osteoarthritis (OA), little is known about the effectiveness of varus bracing for lateral knee OA after ACLR. Purpose: To determine the immediate effects of a varus unloader knee brace on gait biomechanics in people with lateral knee OA and valgus malalignment after ACLR. Study Design: Controlled laboratory study. Methods: Nineteen participants who had undergone primary ACLR 5 to 20 years previously and had symptomatic and radiographic lateral knee OA as well as valgus malalignment were included. Three-dimensional gait analyses were conducted during walking under 3 test conditions: (1) no brace, (2) unadjusted brace (sagittal plane support with neutral frontal plane adjustment), and (3) adjusted brace (sagittal plane support with varus adjustment). Knee, pelvis, hip, and ankle kinematics and moments data were statistically analyzed using repeated-measures analysis of variance ( alpha= 0.05). Results: Compared with walking with no brace, the adjusted brace significantly increased peak knee flexion angle (mean difference [95% CI]: 3.2 degrees [1.3 degrees to 5.0 degrees]) and adduction angle (1.7 degrees [0.8 degrees to 2.6 degrees]) and reduced peak internal rotation angle (-3.0 degrees [-4.0 degrees to -2.0 degrees]). Significant increases in peak knee flexion moment (0.14 Nm/kg [0.06 to 0.20 N center dot m/kg]), adduction moment (0.10 N center dot m/kg [0.07 to 0.14 N center dot m/kg]), and external rotation moment (0.01 N center dot m/kg [0.00 to 0.02 N center dot m/kg]) were observed with the adjusted brace. The adjusted brace also reduced peak hip adduction angle (-1.29 degrees [-2.12 to -0.47]) and increased peak hip adduction (0.17 N center dot m/kg [0.04 to 0.31 N center dot m/kg]) and external rotation moments (0.09 N center dot m/kg [0.03 to 0.14 N center dot m/kg]). There were no significant differences between the adjusted and unadjusted brace conditions, except for knee internal rotation angle, where the adjusted brace produced significantly greater reductions relative to the unadjusted brace (-1.46 degrees [-1.98 to -0.95]). Conclusion: Irrespective of frontal plane adjustment, the varus unloader brace produced immediate modulations in sagittal, frontal, and transverse plane joint angles and moments in younger individuals with lateral knee OA and valgus malalignment after ACLR. Clinical Relevance: The varus unloader brace may have the potential to mitigate abnormal knee joint mechanics associated with the development and progression of lateral knee OA after ACLR.