The main findings of this study demonstrate that in the context of ACL injury, the PCL angle has a normal value, particularly in the acute phase, and a direct negative correlation exists between anterior tibial translation (both medial and lateral) and the PCL angle. Furthermore, women demonstrate higher values (130° vs. 127° compared to males).

Our study's result somewhat contrast with the current literature; only three patients reported a PCL angle of less than 105°. Recent literature has indicated that a PCL angle of less than 105° is considered positive evidence for an ACL tear. This discrepancy may be attributed to the fact that nearly all patients evaluated in this study suffered from acute injuries, and the time between trauma and MRI was very short [20].

According to our study, in 1998, Dimond et al. compared MRI findings in 87 patients with acute and chronic ACL tears. The study revealed that increased anterior curvature or bowing of the PCL was more pronounced in cases with chronic ACL tears. The mean value of the PCL bowing ratio for cases with chronic ACL tears was 0.47 compared to 0.37 for cases with acute ACL tears (p = 0.013) [21].

Similarly, Sevim et al. examined the impact of prolonged ACL deficiency on the PTS and the sagittal morphology of the proximal tibia, revealing that the knees of patients with chronic ACL deficiency (5 years) exhibited elevated medial and lateral PTS in comparison to the unaffected contralateral knees. Consequently, while strategizing ACL repair for patients with a prolonged history of ACL deficit, it is imperative to precisely assess the preoperative PTS [22].

Numerous research have examined the behavior of the PCL in knees lacking in ACL, utilizing these characteristics as a reference. Gali et al. evaluated the posterior cruciate ligament inclination angle (PCLIA) in MRIs of persons with and without ACL injuries, positing that PCLIA measurement using MRI may function as an adjunctive technique for identifying ACL insufficiency. The scientists concluded that the PCLIA was markedly elevated in people with ACL injuries. The assessment of this angle by MRI imaging may facilitate the identification of ACL insufficiency, hence aiding in a tailored and accurate treatment strategy for ACL injuries [23].

Likewise, Oronowicz et al. sought to ascertain whether the posterior cruciate ligament–posterior cortex angle (PCL–PCA) correlates with the chronicity of ACL rupture, meniscal condition, preoperative knee laxity, or imaging indicators such as the lateral collateral ligament sign or the PTS in knees with ACL injuries [10].

A total of eighty-two participants enrolled in this trial. The median PCL–PCA was 16.2°, with a significant difference between acute (18.4°) and chronic (10.7°) injuries (p < 0.01). The median PCL–PCA was markedly reduced by 4.6°. No substantial correlation was identified between PCL–PCA and meniscal condition, PTS, or preoperative anterior knee laxity (Lachman, pivot shift, and ATT measured in millimeters). The findings corroborate the idea that PCL–PCA and the LCL sign may serve as valuable indicators of knee decompensation progression following an ACL injury. [10].

In 2022, Siboni et al. endeavored to verify a novel MRI technique for quantifying the buckling phenomenon of the PCL, indicative of anterior tibial translation, by assessing its reliability and accuracy against established methods in ACL-deficient knees [11]. The evaluation of the curvature of the anterolateral bundle of the posterior cruciate ligament (PCL) was conducted using T2 sagittal MRI slices through three methodologies: (1) the PCL angle (PCLA), (2) the PCL inclination angle (PCLIA), and (3) an innovative approach: the PCL-posterior cortex angle (PCL–PCA), which denotes the angle between the vertical segment of the PCL-ALB and the posterior diaphyseal cortex of the femur. The inter- and intra-observer reliability was assessed for each method. The capacity to differentiate between ACL-deficient and ACL-intact knees was assessed utilizing ROC curves. Compared to previously described approaches, the PCL–PCA was the most dependable and precise technique for assessing the PCL buckling phenomena on MRI in ACL-deficient knees. It provides a straightforward and impartial approach for monitoring ACL-injured patients and is thus advisable for regular use [11].

Analyzing our results, it is possible to highlight a difference in anterior tibial translation between acute and chronic patients. This result aligns with current literature; recently, Cance et al. compared the static ATT value in a control population with that in a population with an isolated ACL injury, reporting a reference static ATT value of 1.31 mm in a non–ACL-injured cohort, which was lower than in the ACL-injured cohort (mean, 2.27 mm) [24].

This anterior lateral tibial translation can have important clinical implications, as reported by Lian et al. The authors determined whether static tibial subluxation, as measured on MRI, is associated with the grade of rotatory knee laxity in ACL-deficient knees [25].

The authors determined that two separate groups exhibiting rotatory knee laxity indicated that static anterior subluxation of the lateral tibial plateau measuring 2.95 mm or more correlated with high-grade rotatory knee laxity, and each millimeter increment in lateral tibial plateau subluxation corresponded to a 1.2-fold increase in the likelihood of high-grade rotatory knee laxity. Anterolateral displacement of the tibial plateau on MRI was not independently correlated with severe rotatory knee laxity when accompanied by a lateral meniscal injury. Preoperative static measures may assist in forecasting high-grade rotatory knee laxity and enhancing the criteria for personalized knee surgery. [25].

Finally, our study showed a statistical difference in PCL angle between males and females; several factors may contribute to this finding. First, as described by Gupta et al. in a cadaveric study, the length of ligaments was found to be greater in males than in females. Thus, in cases of anterior tibial translation, the shorter ligaments in women lead to a different angle compared to males [26].

Another factor relates to differences in laxity associated with gender; Boguszweski et al. confirmed that female knees demonstrated significantly increased laxity and reduced stiffness compared to males [27].

Finally, as reported by Chandrashekar et al., female ligaments exhibit lower mechanical properties when compared to males [28].

This study has limitations. Initially, we did not link the MRI measurement data with clinical or arthroscopic evaluations of the individuals studied, as the diagnosis was solely based on MRI analysis. Nonetheless, the radiologists conducting the assessments evaluated MRI scans of instances with a definitive diagnosis of either damaged or intact ACL. The data included only cases of unequivocally injured ACLs, so removing those that could be classified as partial injuries. Nonetheless, we can investigate the mechanical properties of the residual ACL fibers after partial injuries. Future research is essential to elucidate the characteristics and biomechanical properties of partial ACL injuries, as well as the implications of partial ACL insufficiency.