Effect of a functional knee brace on knee flexion and extension strength after anterior cruciate ligament reconstruction

Abstract

Birmingham TB, Kramer JF, Kirkley A. Effect of a functional knee brace on knee flexion and extension strength after anterior cruciate ligament reconstruction. Arch Phys Med Rehabil 2002;83:1472-5. Objectives: To investigate the effect of a knee brace on knee flexion and extension muscular strength of patients after anterior cruciate ligament (ACL) reconstruction and to evaluate whether the effect of the brace depends on patient symptoms and muscular strength. Design: Repeated measures. Setting: A university-based outpatient orthopedic clinic and musculoskeletal assessment laboratory. Participants: Twenty-seven patients (14 women, 13 men; mean age, 28±11y) having undergone arthroscopically assisted ACL reconstruction by using a semitendinosus and gracilis autograft. Intervention: A custom-fit ACL functional knee brace. Main Outcome Measures: The brace effect was calculated as the change in peak torque observed with the brace, expressed as a percentage of peak torque observed without the brace, during isokinetic concentric knee flexion and extension movements performed at 90°/s. Patient symptoms were quantified by using a disease-specific health-related quality of life questionnaire. Results: Knee flexion strength decreased significantly with the brace (mean brace effect=−7.3%, P<.05). The brace effect during knee flexion varied considerably (−52% to 47%) and was significantly related to peak torque observed without the brace (r=−.50, P<.01). All other comparisons and correlations were not significant. Conclusions: These findings suggest that brace effects depend on patient strength. A brace may inhibit knee flexion strength of stronger patients, yet result in no change or even improvements in strength of weaker patients. Future research is required to further elucidate which patients may derive most benefit or detriment from bracing. © 2002 by the American Congress of Rehabilitation Medicine and the American Academy of Physical Medicine and Rehabilitation