## 4 Discussion  
This study examined the knee joint biomechanics of female basketball players during the push-off and landing cushioning phases of a pull-up jump shot while wearing knee braces with varying stiffness levels. The results revealed significant differences in knee joint flexion and adduction angles, range of motion in the sagittal and coronal planes, knee adduction moment, positive work, and joint contact force between conditions with and without high-stiffness knee braces. As hypothesized, the knee flexion angle was inversely related to knee brace stiffness, though significant differences were only observed in the range of motion in the horizontal plane between the low- and high-stiffness braces. Previous studies had shown that a larger knee flexion angle at the IC moment increased the risk of soft tissue injuries, including ACL injuries, meniscal tears, MCL injuries, and chronic knee osteoarthritis [32]. Smaller flexion angles, on the other hand, can reduce the load on the ACL. A study that simulated the pull-up jump shot motion also indicated that female athletes exhibit a larger knee joint flexion angle upon landing compared to male athletes [33]. According to [PERSON]'s research, when the knee flexion angle of females increased from 22.3\({}^{\circ}\) to 27.6\({}^{\circ}\), the angle between the patellar tendon and the tibia decreased from an average of 19\({}^{\circ}\) to 17.4\({}^{\circ}\), which significantly reduced the load on the ACL [34]. Additionally, during the push-off and landing cushioning phases, knee extensors must generate greater positive work to increase jump height. Joint work reflects the timing, magnitude, and energy transfer by muscles, ligaments, and other tissues [35]. This work mainly depends on muscle fibers' contractile power during rapid contractions. Our study found that knee joint work across both phases of the pull-up jump shot followed a consistent pattern. At a given jump height, greater positive joint work indicated higher demands for kinetic energy and speed. Notably, knee joints with high-stiffness knee braces exhibited lower flexion moments and positive work, suggesting that high-stiffness braces may reduce the muscle force required by the knee joint during takeoff after landing, potentially lowering injury risks [36]. Our study revealed that compared to no-stiffness and low-stiffness knee braces, wearing high-stiffness knee braces significantly reduced the abduction angle of the knee joint. Consequently, knee braces can help prevent patellofemoral pain syndrome, with high-stiffness braces being more effective than low-stiffness ones. Furthermore, high-stiffness knee braces enhance frontal plane stability of the knee joint, reduce the pressure on the medial meniscus and medial cartilage, and lower the risk of injury. It had been shown that for every 1\({}^{\circ}\) increase in knee abduction angle, the knee joint load increased by 1.7 Nm [34]. Previous studies had demonstrated a correlation between reduced knee abduction and alleviated osteoarthritis pain [37], while excessive tibial external rotation may lead to degeneration of the knee's soft tissues, contributing to chronic knee osteoarthritis. This suggested that wearing knee braces may help prevent osteoarthritis and alleviate knee pain [38]. The elastic constraint provided by low-stiffness knee braces is weaker than that of high-stiffness braces, resulting in a less effective reduction in knee valgus angles. However, it should be noted that while high-stiffness knee braces effectively decrease valgus angles and reduce valgus loading, they may compromise the knee joint's ability to dissipate and absorb ground reaction forces. This limitation could lead to the transmission of impact forces to more proximal segments of the body. During the push-off and landing cushioning phases, the ROM of the knee angle in the sagittal plane was positively correlated with knee brace stiffness. Higher stiffness levels in the knee braces resulted in greater knee joint ROM throughout these phases.