Evaluation of Vastus Medialis Muscle Inhibition After Anterior Cruciate Ligament Repair with Superficial Kinesiological Electromyography

Background: The Anterior Cruciate Ligament (ACL) is essential for knee stability and dynamic movement, ACL are injuries common, especially among athletes. ACL reconstruction surgery aims to restore knee function, and post-surgical rehabilitation is crucial for recovery. This study focuses on the activation timing of the quadriceps and hamstring muscles during functional tasks in patients post-ACL surgery to enhance rehabilitation strategies. Methods: This cross-sectional, quantitative study included 30 male participants who underwent ACL reconstruction using semitendinosus and gracilis grafts. Electromyographic (EMG) data were gathered using Noraxon Ultium EMG sensors and analyzed with Noraxon MyoResearch XP. Muscle activation timings for vastus medialis oblique (VMO), vastus lateralis (VL), semimembranosus (SM), semitendinosus (ST), and biceps femoris (BF) were recorded during single-leg squat tasks. Results: Significant differences were observed in the onset times of VMO relative to VL during both eccentric and concentric tasks (F1,30 = 9.42, p < .001). No significant differences were noted between eccentric and concentric tasks for SM and ST (F1,30 = 0.00, p > .5). VMO activation was consistently delayed and less intense compared to VL and the hamstrings, with a significant delay in onset (p = 0.0013). Conclusions: This study highlights significant neuromuscular differences in the activation timing and intensity of the VMO and VL in ACL surgery patients. The delayed and less intense activation of VMO indicates the need for targeted rehabilitation to address these imbalances, ensuring proper muscle coordination and knee stability post-surgery. Rehabilitation should focus on exercises to improve VMO activation and timing, along with neuromuscular training for coordinated muscle activation during dynamic tasks. Future research should involve larger, diverse populations and advanced imaging techniques to better understand neuromuscular adaptations post-ACL surgery.