What is the main function of the knee joint?

The main function of the knee joint is to allow movement while bearing weight. This joint is a crucial component of the human body, providing the necessary flexibility to perform various activities such as walking, running, jumping, and squatting, all while supporting the weight of the body. The knee's unique structure, which includes ligaments, tendons, cartilage, and bone, enables it to perform flexion and extension motions while maintaining stability when under load.

While other options mention important aspects of the knee, they do not encompass its primary function as comprehensively as the ability to permit movement under weight-bearing conditions. The knee must effectively balance mobility with stability, which is essential for maintaining upright posture and facilitating locomotion.