Electromyographic analysis of anterior cruciate deficient knees with and without functional bracing during lunge exercise.

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.