Background and aim of the work Anterior cruciate ligament (ACL) reconstruction is an extremely frequent surgery. The analysis of anatomical factors is becoming increasingly important and the study of clinical, arthroscopic and radiological methods to evaluate and understand them aims to positively affect the patient's outcome. This work aims to analyze the role of Lateral Posterior Tibial Slope (LPTS) as a potential risk factor for ACL reconstruction failure Materials and Methods At the Clinic of Orthopedic of Udine, between November 2018 and August 2020, 47 revisions of the ACL were performed. We analyzed MRI scans with particular attention to the LPTS. Patient images were analyzed by a single senior orthopedic surgeon who was blinded to patient history, age and gender. Results Comparing with a value reported in literature as normal (LPTS estimated 6.5°) we see how the difference between the average LPTS values in the sample is significantly higher than the normal values (P <.0001). Furthermore, in our cohort, females show a LPTS significantly higher than males (11,8° vs 8,7°; P <.005). Conclusion The data collected show how an increased posterior lateral tibial slope can be correlated with a higher risk of ACL reconstruction failure. The results are coherent with the literature. Our analysis is absolutely preliminary, but it is intended to be the starting point of a path that allows us to think of the reconstruction of the ACL as an intervention to be planned more carefully based on the individual characteristics of the patient.