## 4 Discussion
The multidirectional load placed on the ACL by CM necessitates a comprehensive examination of knee joint biomechanics in various planes for an improved understanding of ACL mechanics. Notably, significant differences in frontal and coronal plane joint displacement, forces, and moments were observed after the running training load, indicating a less stable knee joint that could increase the risk of knee injury. It has been recommended that strengthening the knee extensor and flexor muscles can help to reduce overload injury risk of ACL during the knee flexion and extension during CM [60]. The method presented in this study can be used for individual assessment of ACL mechanics during CM enabling to monitor changes in ACL strain over time. This can reflect the athlete's improvement in neuromuscular control after a targeted training regiment, and enable to check how effectively can it reduce ACL strain during CM [61]. Most of knee extensor and flexor muscles are biaarticular muscles thus fatigue of the muscles affects the hip joint as well. We also observed changes in hip kinematic characteristics, which may have an impact on knee joint mechanics and indirectly affect ACL mechanics. Therefore, targeted strength training of the hip joint muscles could potentially aid in reducing the risk of ACL injuries [62]. The PCA revealed notable distinctions in knee moment during the AA rotation stage, knee angle during FE (as shown in Figure 7D), and EI rotation (as depicted in Figure 7E), in addition to knee contact force in both the sagittal (Figure 7G) and coronal (Figure 7I) planes, when performing CM. This will hopefully serve as the key determinant in distinguishing between high and low levels of ACL strain. The primary function of the ACL is to resist anterior translation movement of the tibia with respect to the femur [63], but movements in the frontal and transverse planes can also affect ACL loading [64; 65; 66]. Our results showed more internal knee moment at the beginning, which may have a substantial impact on ACL loading. During CM, the initial acceleration of the body, induced by its inertia, causes it to continue moving forward. However, the generation of more inward moment at the knee joint creates a counteracting force against the inertia, providing additional support to the body. The generated inward moment at the knee joint during cutting may also increase the risk of soft tissue injury due to insufficient internal force, as the knee joint is not able to counteract the generated moment effectively [67]. During change of direction the body is required to accelerate into a different direction, which can result in an increased knee abduction moment which may impose a significant load on the ACL [68]. Limiting the axial rotation of the tibia could potentially affect the knee's natural movement when a valgus moment is applied. Therefore, in this study, we did not constrain the kinematics of the knee joint, which increased the accuracy of the model in calculating the ACL strain. The findings of this investigation reveal that variations in knee angle during all CM conditions across all three planes cause a significant influence on the mechanical loading of the ACL. The quick transition from internal to external rotation during athletic movements can lead to an imbalance in muscle function [69], which in turn may result in a great increase in knee joint loading and increase the risk of injury. This assumption can be supported by previous reports that also indicate that an increase in the knee abduction angle can have a significant impact on the risk of ACL injury [19; 70]. While the relative importance of non-sagittal loads to ACL loading is still a topic of debate [71], it is widely accepted that anterior and posterior shear forces can lead to loading and unloading of the ACL, respectively [64; 72].