Background: The use of functional knee braces for returning to sports or during demanding activities following anterior cruciate ligament rupture is common; yet despite being commonly prescribed, its mechanism of action remains unknown.
Objectives: To examine the effect of functional knee braces on mean muscle activity when performing lunge exercises.
Study design: Pre-/post-test (within-subject research design).
Methods: A total of 10 male participants with unilateral isolated anterior cruciate ligament deficiency participated. Electromyographic activities of six muscles around the knee were recorded during lunge exercises, with and without wearing a custom functional knee brace. The lunge cycle movement was subdivided into three phases: eccentric, isometric, and concentric.
Results: The quadriceps and hamstrings were no different in the braced and unbraced conditions. When braced, the mean amplitude of the medial gastrocnemius was significantly lower throughout the whole movement (p = 0.01) and during the concentric (p = 0.006) and eccentric (p = 0.028) phases, but not within the isometric phase. The lateral gastrocnemius was found to have lower mean amplitude in the isometric phase (p = 0.044).
Conclusion: With its origin on the medial femoral condyle, perhaps reduced medial gastrocnemius activity may better guide knee rotation and assist the joint achieving a healthier kinematic pattern.
Clinical relevance: Lower medial gastrocnemius activity may facilitate lower medial compartment contact pressure, for which greater loading is known to increase the risk of osteoarthritis in anterior cruciate ligament-deficient (ACLD) knees. However, further research is needed.
Keywords: Electromyography; anterior cruciate ligament; brace.
© The International Society for Prosthetics and Orthotics 2014.