## 4 Discussion
Previous studies on basketball-specific movements had pointed out that in the pull-up stop jump shot, the athlete's front foot often lands in an \"external rotation\" posture; that is, the knee joint is abducted. Both low-stiffness and high-stiffness knee braces effectively mitigate excessive knee joint abduction, prevent misalignment of the femoral-tibial force vector, and reduce ACL load. This study found that both types of braces decreased the maximum knee flexion angle compared to conditions without a knee brace, aligning with findings from previous research [49]. Therefore, wearing knee braces with a certain level of stiffness can help prevent patellofemoral pain. This suggested that high-stiffness knee braces can enhance knee joint stability in the coronal plane, reduce the pressure on the medial meniscus and medial cartilage, and lower the risk of injury [50]. In [PERSON]'s study it was shown that during vertical jumping movements, the external rotation moment at the knee also increases the risk of ACL injuries [51]. Wearing both low-stiffness and high-stiffness knee braces effectively enhances knee stability during the landing phase, helping to prevent injuries associated with excessive knee abduction. However, the differences between low-stiffness and high-stiffness braces are minimal, as both types significantly reduce the knee abduction angle during the two phases. This finding suggested that high-stiffness knee braces can improve frontal plane stability of the knee joint, reduce pressure on the medial meniscus and medial cartilage, and thereby lower the risk of injury [34]. Previous studies had indicated that the reduction in knee abduction is associated with a decrease in the severity of knee osteoarthritis pain [52]. This meant that high-stiffness knee braces can prevent knee osteoarthritis and alleviate pain, making them suitable for athletes with existing knee injuries in high-intensity basketball games. The hypothesis of this study proposed that wearing high-stiffness knee braces could reduce the indirect contact forces on the knee joint; however, the experimental results were contrary to this assumption. This may be because knee braces with stiffness levels (both low and high) somewhat restrict the natural ROM of the knee joint. Such restriction could lead to alterations in movement patterns, thereby increasing the contact force within the joint. When the knee joint is restricted by a stiff brace, the range of motion is reduced, concentrating forces in a specific area and resulting in higher local contact forces. This finding is consistent with previous research [53]. Further studies are needed to balance the support effects of knee braces with their interference in the joint's natural motion to avoid potential joint overload caused by the brace. This issue remains an area worth deeper exploration in future research. Several limitations of the current study should be acknowledged. First, this experimental study was conducted in a laboratory setting, which may not fully replicate the pull-up jump shot movements and intensity of the athletes in real game scenarios. Future research should aim to explore real game environments and investigate the effects of knee braces with different stiffness levels on lower limb biomechanics using more diverse methodologies. And as a tool to protect the knee joint, there is also a certain uncertainty in the frequency of wearing knee braces. Whether long-term wearing of knee braces is more helpful for the knee joint requires more detailed long-term studies. Additionally, the use of instruments such as infrared reflective marker balls placed on the subjects may have influenced their performance during exercise. Future studies could monitor athletes during actual games using wearable devices to more accurately investigate the knee joint injury mechanisms in female basketball players. And the subjects of this experimental study were amateur female basketball players, which is a limitation for most female basketball players.