Relationship Between Preoperative Arthrogenic Muscle Inhibition Grade and Knee Functional Outcome Following Anterior Cruciate Ligament Reconstruction

Introduction Arthrogenic muscle inhibition (AMI) is a reflexive reduction in quadriceps activation following knee injury that may persist into the perioperative period. Decreased preoperative quadriceps function is thought to contribute to poor postoperative knee functional outcomes. This study aimed to determine the relationship between preoperative AMI grade and International Knee Documentation Committee (IKDC) score three months after anterior cruciate ligament (ACL) reconstruction. Materials and methods This single-center retrospective cohort study included 82 adults undergoing ACL reconstruction stratified into two groups - one comprising patients with isolated ACL injury (n = 28) and the other group comprising patients with concomitant meniscal injury (n = 54). Preoperative AMI was graded using the Scientific Anterior Cruciate Ligament Network International (SANTI) clinical classification, and the primary outcome was the IKDC Subjective Knee Form score at three months postoperative. Preoperative AMI grade was modeled as an ordinal variable in multivariable linear regression to assess its association with three-month IKDC, adjusting for preoperative IKDC and time since injury. The same regression model was first applied to the whole cohort and then repeated separately within the isolated ACL and ACL with meniscal injury subgroups. Statistical analyses were performed using IBM SPSS Statistics for Windows, version 29.0 (IBM Corp., Armonk, NY, USA). Results Preoperative AMI grade for all 82 patients showed weak negative correlation with three-month IKDC score (r = −0.27, p = 0.014). In adjusted regression, higher AMI grade was associated with lower three-month IKDC (β = −1.51; 95% confidence interval (CI), −2.46 to −0.56; p = 0.002). In the ACL plus meniscal injury subgroup, the association was more pronounced (β = −2.43; 95% CI, −3.61 to −1.25; p < 0.001). No significant association was observed in isolated ACL (β = +0.80; 95% CI, −1.07 to +2.66; p = 0.386). Conclusions Higher preoperative AMI grade was associated with lower three-month IKDC after ACL reconstruction. The association was stronger in patients with concomitant meniscal pathology. Preoperative AMI grading may identify patients at risk of poorer early functional recovery and support the rationale for targeted preoperative neuromuscular rehabilitation.