# Finite Element Analysis of a Novel Approach for Knee and Ankle Protection during Landing
## 4 Discussion  
During a half-squat landing, a GRF that is several times the BW is transmitted from the planta and ankle up to the shank and knee [5]. Furthermore, injuries that occur at the moment of landing are a direct result of excessive GRF [27, 28]. Therefore, how to effectively reduce GRF has attracted the attention of scientists. In previous studies, the principle of protection for both knees and ankles focused on reducing the incidence of injury by limiting joint ROM [1, 8, 13, 14, 15]. Although such braces can provide beneficial protective effects, they also affect the user's performance [16, 17]. As a matter of course, a novel approach, which can not only counteract the action of the GRF, but also reduce the constraint on lower-limb movement, is essential for knee and ankle protection during landing. In this study, an FE model of the lower extremity was developed, and an anatomically detailed representation of the ankle and knee was constructed, with the reactions and tensions of soft tissue, ligamentous, and adjacent bony structures taken into consideration. Then, the biomechanical responses of the ankle and knee before and after wearing the brace were investigated and used to evaluate its protective performance. The validation process was carried out in two steps, first for the ankle and then for the knee. The simulation was compared to previous experimental and computational results with similar settings to this study [25, 26]. It can be seen that the deviations were only 0.05% and 0.08%, compared to [PERSON]'s results. As the difference was less than 1%, it was sufficient to validate the mechanical similarity of the ankle. Likewise, the results of anterior tibial translation, used to validate the mechanical similarity of the knee, were also consistent with the literature. It should be noted that our simulation results were higher than those of the cadaveric study. This difference may have been due to a decrease in system stiffness attributed to the simplification of ligaments and other soft tissues [29, 30]. The tibia is the main weight-bearing bone of the shank, and the articular surface between the tibia and talus is the main load-bearing location of the ankle [7]. As can be seen from the results of Figures 3 and 4, the peak von Mises stress of the inferior articular surface of the tibia increased visibly with increasing jump height. This is understandable, since the GRF is known to increase significantly with an increase in jump height [31], and the stress on the human body increases accordingly on the basis of the principle of inverse dynamics [32]. More importantly, when landing from a large height (0.8 m and 1.2 m), stress concentration occurred in vulnerable areas such as the medial condyle, which definitely increased the risk of compression fractures [33, 34]. Comparatively, after wearing the brace, the stress peak decreased, thereby reducing the incidence of local fractures [35]. However, the pattern of stress distribution did not change, indicating that the semi-rigid  
Figure 6: The medial contact area (MCA) and lateral contact area (LCA) between the menisci and articular cartilages before and after wearing the brace. brace at the ankle joint reduced stress by diverting some of the GRF that would otherwise be experienced by the human body, whereas it did not affect the way in which load was distributed over the impacted area. This portion of the transferred GRF was transmitted upward and gradually absorbed by the brace itself; in a practical device, hip components can also be added to help absorb impact energy. In addition to stress fracture, ankle inversion and version represent common injuries that cannot be ignored [36]. Due to the special anatomical structure of the talus [37], which is wide in the anterior region and narrow in the posterior region, the foot is prone to varus and valgus when subjected to a high horizontal impact.