Tibial Subluxation of Lateral Compartment Is Associated With High-Grade Knee Laxity in Patients With Anterior Cruciate Ligament Deficiency

High-grade knee laxity and excessive anterior tibial subluxation (ATS) are correlated with poor clinical outcomes in patients with anterior cruciate ligament (ACL) deficiency and share similar risk factors; however, the association between excessive ATS and high-grade knee laxity remains unclear. A total of 226 patients who underwent ACL reconstruction between May 2018 and March 2022 were analyzed in the present study, including 113 patients with preoperative anterior drawer test, Lachman test, or pivot-shift test grade 3 under anesthesia in the high-grade group and 113 patients matched in the low-grade group. The ATS of medial and lateral compartments (ATSMC and ATSLC) were measured on magnetic resonance imaging with patients relaxing the quadriceps in the supine position under no anesthesia. The optimal cutoff values of ATSMC and ATSLC for high-grade knee laxity were determined using receiver operating characteristic curves. Univariate and multivariate logistic regression analyses with stratification were performed to identify the association between excessive ATS and high-grade knee laxity. The high-grade group had a longer time from injury to surgery, higher rates of medial meniscus posterior horn tear (MMPHT), lateral meniscus posterior horn tear (LMPHT), and anterolateral ligament (ALL) abnormality, as well as larger lateral tibial slope, ATSMC, and ATSLC as compared with the low-grade group. The optimal cutoff value was 2.6 mm (sensitivity, 52.2%; specificity, 76.1%) for ATSMC and 4.5 mm (sensitivity, 67.3%; specificity, 64.6%) for ATSLC in predicting high-grade knee laxity. After adjusting for the covariates, ATSLC ≥4.5 mm (odds ratio [OR], 2.94; 95% CI, 1.56–5.55; P =.001), MMPHT (OR, 2.62; 95% CI, 1.35–5.08; P = .004), LMPHT (OR, 2.39; 95% CI, 1.20–4.78; P =.014), and ALL abnormality (OR, 2.09; 95% CI, 1.13–3.89; P =.019) were associated with high-grade knee laxity. The association between excessive ATSLC and high-grade knee laxity was validated in both acute and chronic ACL-injured patients. Excessive ATSLC is associated with high-grade knee laxity in ACL-deficient patients with a predictive cutoff value of 4.5 mm. This study may help surgeons estimate the degree of knee instability more accurately before anesthesia and facilitate preliminary surgical decision-making, such as appropriate graft choices and consideration of extra-articular augmentation.