Background and Aims: Posterior tibial slope (PTS) is a key anatomical determinant of knee stability following anterior cruciate ligament (ACL) reconstruction. An increased PTS amplifies anterior tibial translation under load, placing elevated mechanical demand on native ligaments and reconstructed grafts. This review aims to synthesize current evidence on PTS measurement, biomechanical relevance, risk stratification, and surgical management in ACL instability and graft failure. Materials and Methods: A narrative review of the literature was conducted, focusing on key biomechanical and clinical studies addressing PTS in the context of ACL injury and reconstruction. Studies examining measurement methodology, imaging modalities, rotatory instability, and slope-reducing osteotomy were included. Results: Increased PTS is consistently associated with higher ACL graft failure rates and reduced long-term survivorship. Risk increases continuously rather than at a fixed threshold. Lateral PTS and lateral-medial asymmetry correlate more strongly with rotatory instability than mean PTS alone. Accurate measurement requires standardized long lateral radiographs, as imaging technique significantly affects values. Slope-reducing osteotomy combined with soft-tissue reconstruction effectively restores stability in revision cases. Conclusion: PTS assessment should be routine in revision ACL surgery and considered in high-risk primary cases. Surgical decision-making should be individualized, integrating PTS within a multifactorial risk profile rather than applying fixed numerical thresholds.
Pichler et al. (2026) studied this question.