Abstract: BACKGROUND: Knee ligaments are an important part of maintaining the stability of knee joint movement, which is very vulnerable to injury during exercise, and sports knee braces are often used to prevent knee injuries, but their protective performance is not clear.  
OBJECTIVE: A finite element model of the knee joint of a healthy adult and a sports knee brace model were established. The finite element method was used to predict the effect of the sports knee brace on the knee joint ligament under different movement states so as to observe the protective performance of different knee braces using Von Mises equivalent stress as the observation index.
METHODS: Using CT medical images of one male health volunteer as the data source, Mimics, Solidworks, and Abaqus software were used to obtain the finite element model of the knee joint and the sports knee brace model. The median epicenter of the femur and the medial condyle was set as the reference point to apply backward 134 N concentration force to the point, to simulate the preclinical drawer experiment, to obtain the biomechanical response of the femur relative displacement and major ligaments, and to verify the effectiveness of the knee model. The displacement load was applied to the sports knee brace, to simulate the state of wearing the knee brace in an upright position and to compare with the clothing stress test results to verify the effectiveness of the knee joint-knee brace model. The 0°, 30° and 60° movements of knee joint flexion were simulated without knee braces and knee braces of two different materials. The stress strains of the anterior cruciate ligament, posterior cruciate ligament, medial collateral ligament and lateral collateral ligament were analyzed under different loads.  
RESULTS AND CONCLUSION: (1) The peak stress of the four ligaments was changed at 0°, 30°, and 60° angles, and after applying 320 N vertical compressive force and 134 N femur backward thrust, compared with bare knee, the peak stress of the anterior cruciate ligament was reduced at 0° and 30°, but the peak stress in the 60° flexion increased. The peak stress of the posterior cruciate ligament increased at 0° flexion and decreased in the 30° and 60° flexion. Peak stress of the medial collateral ligament and lateral collateral ligament was reduced at 0°, 30°, and 60° angles. (2) Conclusion: Different materials of sports knee braces can protect the knee ligaments to a certain extent, but at specific angles will cause additional loads on the anterior cruciate ligament and posterior cruciate ligament, and the results of this study have the positive significance for the biomechanical research of knee ligaments, sports injury protection and the design and production of sports knee braces.

Key words: sports knee braces, ligament, protective performance, finite element simulation, biomechanics