INCIDENCE AND RISK FACTORS FOR ARTHROGENIC MUSCLE INHIBITION FOLLOWING ACL INJURY IN OUR POPULATION

Abstract

Background: Arthrogenic muscle inhibition (AMI), a condition in which the spinal reflex circuits malfunction and the quadriceps muscle is unable to activate, is a common result of anterior cruciate ligament (ACL) injuries. AMI can significantly impede rehabilitation, leading to quadriceps weakness, knee instability, pain, and long-term consequences such as osteoarthritis. Despite its prevalence, AMI is often under-recognized in clinical practice.
Aim: To assess the incidence and identify risk factors for arthrogenic muscle inhibition following ACL injury in our population.
Methods: A prospective cohort study involving 47 participants with acute ACL injury (within 6 weeks of the occurrence) was conducted from January 2021 to December 2022. Visual Analog Scale (VAS) pain scores, International Knee Documentation Committee (IKDC) scores, Lysholm knee scores, Tegner Activity Scale as well as physical examinations were used to evaluate the participants. AMI was evaluated using thigh circumference measurements and ultrasound to assess muscle thickness.
Results: AMI was present in 85.1% of participants (Group A), with 14.9% (Group B) showing no signs of AMI. AMI and knee effusion had a significant correlation (p=0.005), with 70% of the AMI group having knee effusion and only 20% of the non-AMI group having it. In the AMI group, native bandaging was also used more frequently (p=0.01). AMI did not significantly correlate with sex, length of injury, or mode of injury. IKDC, VAS, and Lysholm knee scores and Tegner Activity Scale scores were among the functional outcomes that were significantly lower in the AMI group, highlighting the detrimental effects of AMI on rehabilitation. Ultrasound measurements revealed significant atrophy in quadriceps muscles, with vastus medialis (VM) as well as rectus femoris being most affected and VMO, showing a trend toward significance.
Conclusions: AMI is highly prevalent following ACL injuries, with high pain score, knee effusion and native bandaging use emerging as key risk factors. The study highlights the critical need for early recognition of AMI and addresses it preoperatively and postoperatively with targeted interventions such as neuromuscular electrical stimulation (NMES), proprioceptive training, and strength-building exercises should be prioritized to restore quadriceps function and prevent long-term functional deficits.