The knee joint is one of the most injured joints in the human body due to its anatomical characteristics, the external environment it is exposed to and its functional needs. There are three major categories of knee structures: bony, extra-articular and intra-articular. Bony structures: The articular surface of the medial condyle is longer and narrower than that of the lateral condyle. The long axis of the lateral condyle essentially follows the sagittal axis, and the medial condyle is usually at an angle of approximately 22° to the sagittal plane. The articular surfaces of the knee do not match; in the medial portion, the femoral and tibial articular surfaces are placed in a plane like a wheel, whereas in the lateral portion, they travel like a wheel on a mound. The knee joint is only able to achieve the necessary stability by relying on the coordination of ligaments and other soft tissue structures. Extra-articular tendonous structures: Important structures include: synovial membrane, joint capsule, collateral ligaments and muscle-tendon units that span the joint. 1, The goose foot is the joint stop of the suture, thin femoral muscle, and semitendinosus muscle on the medial aspect of the upper tibia. 2.The iliotibial bundle is the posterior 1/3 of the iliotibial band, which begins proximally at the lateral epicondyle of the femur and ends distally at the lateral tibial tuberosity (Gerdy’s tuberosity). 3, The N muscle has 3 starting points the strongest part of which starts at the lateral femoral condyle, the other two parts start at the fibula (N fibular ligament) and the lateral meniscal ligament). 4. The arcuate ligament is not an independent structure, but rather an aggregate of all fibrous structures originating from the N muscle. Extra-articular ligament structures: The joint capsule and lateral collateral ligaments are the main extra-articular static stabilizing structures. 1.Medial quadruplex complex: It consists of the tibial collateral ligament, the semimembranosus muscle, the goose foot tendon and the posterior oblique ligament part of the posterior joint capsule. 2, Lateral quadruplex complex: there are iliotibial bundle, peroneal collateral ligament, N tendon, and biceps femoris tendon. 3, The medial knee structure is divided into three layers: the first layer is the deep fascia and the calf fascia; the second layer consists of the superficial tibial collateral ligament and its numerous structures on the anterior side, the ligaments of the posterior medial horn, etc.; the third layer consists of the knee capsule and the deep layer of the tibial collateral ligament. 4. The lateral knee structure is divided into three layers: the first layer includes two parts, the iliotibial bundle and its forward expansion, and the superficial biceps femoris and its backward expansion; the second layer is formed by the supporting band of the quadriceps; the third layer is the lateral joint capsule. Intra-articular structures: include the medial and lateral menisci and the anterior and posterior cruciate ligaments. The functions of the meniscus include: diffusing joint fluid, improving nutrition, cushioning shock, deepening the joint, stabilizing the joint, and having a load-bearing or weight-bearing function.