## 4 Discussion
In future works, we will evaluate the effect of adding all the bracket components that could lead to an increase in the protective effect of the bracket. The main displacement of the knee joint was along the Y axis, which represents a hyperextension of the knee. [PERSON] et al. [4] reported that these mechanisms can cause strains on the ACL, MCL, and meniscus that result in a high incidence of injuries to these structures. Hyperextension of the knee was reported as a mechanism of injuries after the leg became pinned after slipping off the motorcycle [3]. Taking into account the maximum Equivalent Von Mises stress into the limb component (Figure 7), it is possible to see that, at 0.2 m/s and 0.9 m/s, the maximum value is reached in both models. This value is located near the distal tibia section (Figures 8 and 9), and could represent an effect due to the fact that the bone structure was resected. Furthermore, by evaluating the distribution of the equivalent Von Mises stress along the bone components, it can be seen that the location of maximum stress corresponds to the resection of the bone components. These results are due to the load condition on the Femur and the specific boundary conditions (with a fixed support imposed on the Tibia end). Thus, these can be considered as edge effects that do not affect the region of interest (around the knee), but also do not provide relevant information. Instead, by evaluating the distribution of the Equivalent Von Mises stress it is possible to see that the most affected segments are the diaphysis (the middle of the long bone) of the tibia and femur for both models. Further analysis should investigate how the different boundary conditions influence the stress of the tibia and femur. The numerical simulations, neglecting the maximum stress due to the resection of the bone, did not show critical stress on the femur with or without a bracket. However, the stress distribution in the diaphysis of the femur could represent a critical condition. In fact, femoral fractures during a motorcross impact were reported by [PERSON] et al. [3]. [PERSON] et al. (2018) described two cases in which motorcross athletes suffered transverse femoral shaft fractures at the proximal edge of their prophylactic knee brackets, and suggested that while traditional knee braces protect the knee, they may also be associated with a femur fracture [3]. This statement that protective gear could cause a specific injury is further historically reported in literature in a series of specific injury patterns that have resulted from adjustments in skiing equipment as mentioned by [3]. Further analysis will concern the evaluation of the hypothesis that the brackets could be because of a femoral fracture, or in general of other fracture of the limb. Another factor that was considered is the pressure generated inside the joint during the impact (Figure 10). By considering the femoral side of the connection element from 0.2 to 0.45 m/s, the pressure is greater in the FE model with a bracket compared to the model without a bracket. This could be due to the bracket stabilization effect in the joint reducing relative lateral movement of the bone. There is indeed a greater pressure in the lateral part of the connection element in the model without the bracket compared to the model with the bracket. Instead, in the second part of the simulation, the pressure is greater in the model without the bracket, and the location of the maximum value is in the lateral part of the connection element. This finding confirms the previous statement that the bracket stabilises the joint, having a protective effect.