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.