Incidence and Risk Factors for Arthrogenic Muscle Inhibition in the Early Postoperative Period After ACL Reconstruction. A Cohort Study From the SANTI Study Group

Background: Arthrogenic muscle inhibition (AMI) is a process in which neural inhibition after injury or surgery to the knee results in quadriceps activation failure and knee extension deficit. A recent study showed that AMI occurs in over half of patients with acute ACL injuries. Purposes: To (1) determine the incidence of AMI within the 6 weeks after an anterior cruciate ligament reconstruction (ACLR) and (2) identify the risk factors associated with AMI after an ACLR. Study Design: Case-control study; Level of evidence, 3. Methods: Consecutive patients who sustained a primary ACLR between January and October 2023 were considered for study inclusion. Eligible patients underwent a standardized physical examination at 3 and 6 weeks postoperatively. This included an assessment of quadriceps inhibition, identification of any extension deficits, and grading of AMI and its clinical reversibility according to the Sonnery-Cottet classification. Results: = .0149) were associated with a significantly greater risk of AMI at 3 weeks postoperatively. No risk factors were found at 6 weeks postoperatively. Conclusion: AMI occurs in 48.5% of patients at 3 weeks, and 24.2% at 6 weeks after an ACLR. Important risk factors identified for the presence of AMI at 3 weeks postoperatively included the presence of preoperative AMI, immediate postoperative VAS pain score of >7, and absence of preoperative physical therapy.