Anterior cruciate ligament (ACL) rupture is a significant injury prevalent in athletes and individuals engaged in high-impact activities. This chapter aims to overview the complex biomechanics of the knee joint in relation to ACL injury, exploring the dynamic interplay of anatomical structures, mechanical forces, and movement patterns that contribute to ACL integrity or predispose it to rupture. The complex biomechanics of the knee and the essential role of the ACL in maintaining stability are fundamental to understanding the etiology and consequences of ACL injuries. Advances in biomechanical research provide a roadmap for enhancing prevention and rehabilitation strategies, with a focus on restoring the normal kinematics of the knee after ACL rupture. Understanding the biomechanics of the ACL and the knee is essential for the advancement of prevention, treatment, and rehabilitation strategies for ACL injuries.