The knee joint, being the largest and most complex synovial joint in the body, plays a crucial role in weight-bearing and bodily movements. Due to its wide range of motion, the knee joint is highly vulnerable to injury, and damage to it can lead to movement limitations, significant disability, and a reduction in the quality of life. The use of robotics in rehabilitation has attracted significant attention in knee rehabilitation exercises, offering extensive capabilities for functional adaptation of knee movements in injured athletes. This study focuses on the knee joint's musculoskeletal structure and dynamics, using mathematical modeling and simulation to analyze its behavior. The goal of this research is to identify the forces, torques, and reaction forces in the tibiofemoral joint (the connection between the shinbone and femur) to design and develop a rehabilitation device that reduces knee injuries and is suitable for athletes of different weights and heights. In designing this sports device, emphasis is placed on reducing the negative effects of variable forces on the knee muscles, particularly at angles where the forces reach their maximum. The ultimate goal is to reduce the risk of injury in this area. Furthermore, the device should be designed to be adjustable for athletes of different body sizes, which can be achieved by applying standard settings based on the actual forces exerted on the knee. Lastly, a genetic algorithm is used to optimize the lengths of the links and their placement in the mechanism.