The medial collateral ligament of the knee is a thickened portion of the fibrous layer of the joint capsule, which is a flat, wide triangle with a forward-facing base and is divided into two deep and shallow layers. The deep layer is shorter and is part of the joint capsule, the capsular ligament, and is connected medially to the meniscus; the superficial layer is longer and begins near the medial tuberosity of the medial femoral condyle and ends obliquely inward at the medial surface of the upper tibia, with the lower end point at the deep side of the goose palm tendon, medial to the tibial tuberosity, and 2 to 4 cm below the tibial articular surface. The anterior fibers of the superficial layer of the medial collateral ligament are longitudinal and downward, called the anterior bundle; the posterior fibers are shorter, called the oblique bundle, which is divided into the superior and inferior oblique bundles, which intersect the knee joint edge obliquely and inferiorly, respectively. The medial collateral ligament of the knee joint has the function of maintaining joint stability and regulating joint movement, and its tension varies with the position of the joint. In full flexion, the anterior bundle of the ligament is tense and the posterior bundle is relaxed; in half flexion, the anterior and posterior bundles are relaxed, and in full extension, all ligaments are tense. Therefore, the medial collateral ligament is most susceptible to injury in the semi-flexed position of the knee. In addition, when the ligaments are tense, the nerve reflexes cause the muscles around the knee to contract, thus strengthening the stability of the joint. If the ligament is torn at the end or heals in a relaxed state, the knee will lose this neuromuscular reflex and increase joint instability. Acute medial collateral ligament injury A complete rupture should be surgically repaired with sutures to restore stability to the severed end. It is important to emphasize that a rupture of the inferior end of the medial collateral ligament, where the severed end is pulled out of the gap between the goose foot and the tibia, is unlikely to be repositioned by conservative treatment. In addition, the medial surface of the tibia is cortical bone, which has a smooth surface and is difficult to heal with the severed end; therefore, early surgical treatment is even more important. If the medial collateral ligament of the knee is ruptured alone, the ligament should be repaired directly; if it is combined with intra-articular injury, the intra-articular (arthroscopic if available) should be explored and treated first, and then the medial collateral ligament should be repaired. Repair of upper stop and body rupture Repair the broken end directly with a No. 4 silk or polyester braided suture or overlapping suture; if the upper stop rupture is an avulsion rupture, the broken end should be sutured upward (“U” suture or “8” suture) on the periosteum; For avulsions with bone masses, screws or tooth washers can be used to fix the bone masses when they are large, and sutures can be added to fix them when they are small, and holes can be drilled in the bone surface and sutured with polyester braid. Repair of lower stop fracture Because the lower stop is attached to the smooth and hard inner side of the upper tibia, the fracture is mostly avulsion fracture, rarely with avulsion bone block, and its broken end is difficult to be directly fused and fixed, so it is necessary to reconstruct the stop (fixed after embedding the broken end into the bone hole). The method is: in the deep side of the goose foot (horizontal incision of the goose foot into the more convenient operation) at the lower stop of the medial collateral ligament along its direction of travel with a bone drill on the bone surface to open the bone hole to the medullary cavity, and then in the distal end of the bone hole to drill two bone holes with the bone hole, using polyester braided suture to knit the broken end and then introduce the broken end into the bone channel, two sutures through the bone hole to draw tightly knotted fixed. Fractures with avulsed bone blocks can be repaired with in situ fixation using screws with tooth washers. Injuries to the medial collateral ligaments of the knee with ligament superior stops and extended lax healing of the corporal rupture can be repaired with superior stop supination. The size of the bone block is determined according to the width of the ligament and the extent of the attachment, and then the bone block with the ligament attachment is chiseled (usually about 2 cm × 2 cm), and then the ligament is loosened along the anterior and posterior edges of the ligament along with the joint capsule starting from above the ligament until the joint gap level can be tightened by displacing the ligament forward and pulling the bone block upward along with the ligament to tighten the medial collateral ligament (usually upward). The medial collateral ligament is tightened (usually by 1 to 1.5 cm), and the bone is then embedded in the cortical bone and fixed with cancellous bone screws after grooving. In cases where the inferior stop cannot be tightened, the medial collateral ligament can be reinforced with the semitendinosus tendon. The distal end of the semitendinosus tendon is dissected, the distal attachment is preserved, and the proximal end of the tendon is cut off; a longitudinal bone groove is opened above the superior end of the medial collateral ligament at the medial femoral condyle adductor node and the knee is flexed at 30°, and the knee is internally rotated in the medial femoral condyle adductor node. Dynamic reinforcement of the medial collateral ligament: dissect the free semitendinosus tendon without cutting both ends to maintain its continuity. A transverse bony groove is created above the superior stop of the medial collateral ligament at the medial femoral condyle adductor node, and the semitendinosus tendon is tractionally embedded and suspended in the groove. The advantage of this method is to maintain the integrity and continuity of the tendon with the muscle, which in turn allows the tendon to be tensed when the muscle contracts, thus enhancing the stability of the medial knee joint. Postoperative treatment Postoperative cotton leg compression bandage, fixed with adjustable knee brace 20°-30°, 3-4 weeks to start knee gradually flexion and extension functional exercises and weight training, 6 weeks flexion angle over 90°, full weight bearing, 8 weeks flexion angle over 120° and gradually to normal; protective with knee brace for 3 months, strengthen muscle strength training, six months later can resume general sports.