# Mechanical Properties and Characteristics of the
## 4 Discussion  
The major ligaments of the knee joint include the ACL, PCL, LCL, and MCL; however, recently, many researchers have begun to focus on the ALL as a key ligament in orthopedic and anatomical studies of the knee. The ALL is located in the anterolateral region of the knee and assists the ACL. Therefore, it functionally resists the internal rotation and anterior translation of the tibia as a secondary stabilizer, thus reducing rotational laxity and the pivot shift [17; 25; 26; 27]. Biomechanical assessments of the joint using computer simulation have been performed in various ways. The mechanical properties of major ligaments with roles in promoting stability of the knee and other joints should be researched to analyze the joint biomechanics [28]. The ACL, PCL, LCL, and MCL have been highlighted as the main ligaments to test the tensile properties of the knee joint. However, although the ALL was mentioned to have an important role in knee joint movement, a lack of research regarding ALL properties persists. Therefore, we researched the anatomical and mechanical parameters of the ALL, LCL, and MCL and compared them with one another. In this study, the anatomical dimensions of the ALL, LCL, and MCL were measured in the same sample and the mechanical properties of these ligaments were tested using a universal test machine. According to the results of the anatomical dimensions and mechanical properties, the MCL, which showed the greatest values for the ultimate load and stiffness, was also the widest and thickest among the three ligaments. Meanwhile, the ALL, with the lowest ultimate load and least amount of stiffness, was thinner and shorter than the other two ligaments. Previously, some researchers had mentioned that the ultimate load of the ALL might be different according to the anatomical description of the ALL [3; 29]. The mean ultimate load reported by [PERSON] et al., who investigated the properties of the anterolateral knee capsule using nine samples, was 319.7N and, among these nine samples, two knee capsules included the ALL [30]. In the present study, the femoral attachment of the ALL was independent from the anterolateral capsule but, after passing through the joint line, the ALL blended with the capsule. Therefore, when we harvested the ALLs to test the mechanical properties, the tibial attachment was included in some of the capsule structures. The ultimate load of the ALL in this study was 146.6N, which was smaller than the result of [PERSON] et al., who used the anterolateral knee capsule. The results of the ultimate load in other previous studies also involved smaller values than those obtained using the anterolateral knee capsule, but these results were varied, ranging from 49.9 to 204.8 N (Table 6). Among these, the results of not only the ultimate load but also the stiffness and elastic modulus in the study by [PERSON] et al. showed significant disparity with those findings of both this study and other previous ones [20]. Meanwhile, the ultimate load in the study by [PERSON] et al. was similar to that in this study [23], while the results of [PERSON] at al. and [PERSON] et al. were greater than found in this study [21; 22]. The stiffness reported by [PERSON] et al. was also similar to in this study, but the results of [PERSON] et al. and [PERSON] et al. were just 50% of the values recorded in this study. In this study, the most common failure site was the mid-substance (14/21) and there was no instance of failure reported at the femoral attachment. Most failures in the research by [PERSON] et al. and [PERSON] et al. similarly involved the mid-substance (15/15 and 10/14, respectively).