1. Bony structure: It mainly consists of femur (thigh bone), tibia (calf bone) and patella (knee bone). These bones are covered with smooth cartilage, which protects the bone like the surface of a car and achieves regular and smooth frictional movement during activity. 2. Ligamentous structures: There are mainly the medial and lateral collateral ligaments of the knee joint, and the anterior and posterior cruciate ligaments (cruciate ligaments) within the joint. These ligaments serve to connect the above bone structures and maintain the stability of the joint during movement, allowing for regular motion. 3, cartilage structure: In addition to the cartilage on the surface of the bone structure, there is an important structure is the meniscus. It is the lining in the joint space and plays a role in shock absorption and reducing cartilage wear on the joint surface.