Influence of the Medial and Lateral Posterior Tibial Slope on Anterior Tibial Translation During Gait in Anterior Cruciate Ligament–Deficient Knees

Background: The posterior tibial slope (PTS) is a key determinant of knee biomechanics, with increased PTS values identified as a risk factor for anterior cruciate ligament (ACL) injuries and ACL graft failure. While the relationship between PTS and passive anterior tibial translation (ATT) is well-documented, its influence on dynamic ATT during gait remains unclear. Purpose: To evaluate the in vivo association between medial and lateral PTS (MPTS and LPTS, respectively), as well as lateral-medial PTS difference (ΔPTS), with dynamic and passive ATT in ACL-deficient knees compared with contralateral ACL-intact knees. Study Design: Descriptive laboratory study. Methods: A total of 13 patients with unilateral ACL tears undergoing ACL reconstruction at the authors’ orthopaedic sports medicine center were included in the analysis. Dynamic ATT was assessed using a motion capture–based gait analysis system during walking, while passive ATT was measured using a KT-1000 arthrometer. The contralateral ACL-sufficient knees of the participants were used as paired controls. PTS values (MPTS, LPTS, ΔPTS LPTS minus MPTS) were measured from computed tomography. Correlation analyses were performed to evaluate the relationships between PTS parameters and ATT during gait, as well as during passive assessment. Results: MPTS, LPTS, or ΔPTS values did not differ significantly between ACL-injured and healthy knees ( P > .05). No significant correlations were identified in healthy knees or between MPTS/LPTS and ATT in either group.A strong inverse correlation was observed between ΔPTS and dynamic ATT in ACL-injured knees ( r = −0.692; P = .014), particularly during the stance ( r = −0.708; P = .015) and swing phases ( r = −0.775; P = .005). Conclusion: The results suggest that lateral-medial asymmetry of the PTS (ΔPTS) may influence dynamic ATT in ACL-injured knees during gait. A greater LPTS relative to MPTS was associated with reduced dynamic ATT, whereas a lower LPTS relative to MPTS correlated with increased ATT. This directional relationship indicates that slope asymmetry could act as a restraint, potentially limiting anterior tibial shift during dynamic loading. The observed inverse correlation between ΔPTS and dynamic ATT indicates that this asymmetry could act as a restraint, potentially limiting anterior tibial shift. No significant correlations were identified between MPTS or LPTS individually and dynamic or passive ATT. Further studies are needed to validate these findings. Clinical Relevance: Considering the potential influence of lateral-medial tibial slope asymmetry on dynamic knee stability, these findings provide insight into the biomechanical function of the ACL-injured knee during gait.