Objective:To investigate the relationship between distal femoral torsion (DFT) and anterior lateral ligament (ALL) injury in patients with non-contact anterior cruciate ligament (ACL) rupture and correlation between DFT and increased risk of non-contact ACL rupture.Methods:A retrospective case-control study was conducted to analyze the clinical data of 64 patients with non-contact ACL rupture admitted to the First Affiliated Hospital of Chongqing Medical University from May 2017 to March 2022, including 48 males and 16 females, with age ranging from 21 to 46 years [(33.9±10.1)years]. The patients were categorized into ACL rupture group ( n=32) and ACL rupture+ALL injury group ( n=32) according to whether they had concomitant ALL injury or not, and 32 patients with meniscal injury alone were matched according to their gender, age and body mass index as the meniscal injury group. The reference standard for DFT was the surgical posterior femoral condylar angle (sPCA) defined based on the angle between the line through the lateral condylar convexity and the medial condylar groove and the line connecting the bony posterior condyle as measured by MRI. The differences in sPCA were analyzed between overall non-contact ACL ruptured patients and patients in other groups, as well as between patients of different genders. The area under the curve (AUC) of a receiver operating characteristic (ROC) curve was carried out to determine the cut-off value of sPCA, and its correlation with an increased risk of non-contact ACL rupture was analyzed. Results:Overall non-contact ACL ruptured patients′ sPCA [(3.6±1.1)°] was significantly greater than that in the meniscal injury group [(2.4±1.5)°] ( P<0.01). The sPCA in the ACL rupture group [(3.5±1.2)°] and the ACL rupture+ALL injury group [(3.7±1.0)°] were also significantly greater than that in the meniscal injury group (all P<0.05); the ACL rupture+ALL injury group showed a trend of increased sPCA compared with the ACL rupture group, but the difference was not statistically significant ( P>0.05). In all groups and the whole population of the study, sPCA was increased in females compared with males with no statistically significant difference (all P>0.05). ROC curve analysis showed that in the overall non-contact ACL rupture patients, the AUC of sPCA in predicting the rupture risk of ACL was 0.74, with the cut-off value of 2.72°, the sensitivity of 84%, and the specificity of 69%. When sPCA was more than 2.72°, it was significantly associated with an increased risk of non-contact ACL rupture ( OR=11.88, 95% CI 4.08, 33.49). Conclusions:The sPCA is significantly increased in patients with non-contact ACL rupture. However, increased sPCA is not associated with ALL injury and not significantly increased in female patients compared with male patients. When sPCA is more than 2.7°, the risk of non-contact ACL rupture is significantly increased.