Under the action of external force, the joint suddenly moves to one side and exceeds its normal degree of activity, causing the soft tissues around the joint, such as the joint capsule, ligaments, tendons and so on, to tear and injure, known as joint sprain. In mild cases, only part of the ligament fibers are torn, but in severe cases, the ligaments may be completely torn or the ligaments and joint capsule attached to the bone are torn off, and even dislocation of the joint occurs. Joint sprains are most common in daily life, with the ankle joint being the most common, followed by the knee joint and wrist joint. I. Anatomical summary, causes of injury and pathology: The ankle includes the ankle joint and subtalar joint, which is a weight-bearing joint of the lower limb. The former consists of the lower end of the tibiofibula and the upper part of the talus body, and the latter consists of the lower part of the talus and the heel bone. The lower end of the tibiofibula is connected by the internal and external ankle and lateral collateral ligaments, making the ankle joint quite stable. The inner ankle is underlain by the tough deltoid ligament, which stops at the heel bone, talus, and navicular bone, and restricts excessive valgus movement of the foot. The lateral ligaments are the peroneal heel ligament and the anterior and posterior peroneal talocalcaneal ligaments, which are relatively weak and serve to limit the inversion of the foot. Excessive forceful inversion or eversion activities, such as walking on uneven surfaces, falling from heights or landing unsteadily when running or jumping, can cause lateral or medial ligament injuries, partial tear or complete rupture or avulsion fracture. If the early treatment is not proper, the ligaments are overly lax, which can cause ankle instability, easy to cause repeated sprains, and even articular cartilage injury, traumatic arthritis, which seriously affects the walking function. Clinical manifestations and diagnosis: 1. Lateral ligament injury: caused by strong inversion of the foot. Because the lateral ankle is longer than the medial ankle and the lateral ligament is weak, so that the inversion of the foot has a greater degree of mobility, clinically, the lateral ligament injury is more common. Partial tear of the lateral ligament is more common, and its clinical manifestations are lateral ankle pain, swelling, walking limp; sometimes subcutaneous ecchymosis can be seen; the lateral ligament area has pressure pain; when the foot is turned inward, it causes increased pain in the area of the lateral ligament. Complete rupture of the lateral ligament: less common, more obvious local symptoms. Due to the loss of control of the lateral ligament, abnormal inversion mobility can occur. Sometimes a small piece of bone along with the ligament tears away from the lateral ankle, called an avulsion fracture. When the film is taken in the inversion position, the tibial talonavicular joint surface tilt is far more than the normal range of 5-10°, and the joint space on the injured side is widened. x-ray examination shows the avulsion of bone fragments. 2.Injury of medial ligament: It is caused by strong external rotation of the foot and occurs less frequently. Its clinical manifestation is similar to that of lateral ligament injury, but the location and direction are opposite. The manifestation of the medial ligament area pain, swelling, pressure pain, foot externalization, causing pain in the medial ligament area, there can also be avulsion fracture. 3, osteochondral injury: after ankle sprain, it is also easy to appear distal tibial osteochondral injury and talus osteochondral injury, talus osteochondral injury is more common, emergency missed high rate. Osteochondral lesions of the talus (OLT) are often referred to as osteochondritis dissecans or osteochondritis dissecans, osteochondral fracture, osteochondral defect, and osteochondral injury. osteochondral defect (OCD). The use of several different names has caused confusion in the clinical diagnosis of this disease. Osteochondral fracture of the talus does occur after acute trauma to the ankle joint, and a series of pathologic changes such as cartilage degeneration and separation, subchondral bone necrosis, and cyst formation can occur later. There is usually a history of obvious ankle sprain and recurrent ankle swelling after the injury. However, some patients do not have obvious trauma, can also appear the same pathological changes. At this point it is often referred to as exfoliative osteochondritis of the talus. Trauma is the primary cause of talar osteochondral injury. Osteochondral injuries of the talus can occur anywhere on the cartilaginous surface of the talus, but typical injuries are mostly located on the posterior medial or anterolateral aspect of the talar talocalcaneal articular surface. In addition, some scholars have proposed other causes of talus osteochondral injury: hereditary ossification defects, paraphyseal bone formation, vascular embolism, vascular anomalies, spontaneous osteonecrosis, hormonal disorders, endocrine disorders, and abnormal stresses in the limb with poor lines of force. After ankle sprains, most are medial talar lesions. It may be related to the susceptibility of the ankle joint to inversion injury. Some patients will have lateral ligament injury of the ankle joint, which will cause chronic instability of the ankle joint. Treatment: If the injury of lateral ligament is light and the stability of ankle joint is normal, the affected limb can be elevated in the early stage and cold compresses can be applied to alleviate the pain and reduce the bleeding and swelling. 2~3 days later, physiotherapy, closure, external application of medicines for relieving the swelling, pain and blood stasis can be used with proper rest and attention to the protection of the ankle (e.g., wearing high boots, etc.). If the injury is more serious, 5-7 pieces of adhesive tape about 2,5 cm wide can be used from the lower 1/3 of the inner calf through the inner and outer ankle pasted in the middle of the outer calf, and the tape is wrapped with a bandage outside. Keep the foot in the valgus position to loosen the ligaments for healing, and immobilize for about 3 weeks. If the medial ligament injury, the bandage fixed position is opposite. Nowadays, a protective ankle brace or cast is used to immobilize the treatment in order to repair the tissue. If symptoms are severe, or if the ligament is completely ruptured or there is an avulsion fracture, the foot should be immobilized in a short-legged cast boot or a protective ankle brace to keep it in an “overcorrected” position for about 4 to 6 weeks. If the ankle fracture is large and poorly dislocated, it should be incised and internally fixed. If there is a combination of talus osteochondral injury, it should be treated at an early stage, and early MRI is useful for diagnosis. In symptomatic patients with chronic injuries, non-operative treatment is often ineffective and surgery is required. Smaller superficial cartilage injuries can be treated by arthroscopic removal of the cartilage and drilling of the cartilage defect area. However, in larger cartilage injuries or when there is limited necrosis or cystic degeneration of the subchondral bone, simply removing the diseased cartilage will leave a large area of cartilage defect. This will inevitably affect the function of the ankle joint. Foreign literature has used cartilage lesions >1,5 cm as an indication for mosaic osteochondral transplantation and autologous chondrocyte culture transplantation (ACT). For combined injuries should also be treated at the same time. If there is combined lateral ankle instability, reconstruction of the lateral ligament is required. However, in older patients, the cartilage of the knee and ankle joints has degenerated. Or in the ankle cavity tibia distal corresponding site has lesions, not suitable for mosaic osteochondral transplantation. For those who combine with hindfoot deformity should correct the deformity before surgery. If chronic instability of the lateral ankle joint is combined, the lateral ligament should be repaired or strengthened at the same time. Ankle sprains should be treated promptly, otherwise the consequences can be severe, resulting in ankle instability and recurrent sprains, which aggravate other injuries, such as osteochondral injuries. Later treatment is difficult and often requires surgery, so ankle sprains should receive definitive treatment at an early stage to accomplish repair of ligament damage and cartilage damage. Acute sprains should be treated promptly, and the principle is to brake and reduce swelling and dissipate stasis, so that the damaged tissues can be well repaired. Braking is accomplished with casts or protective braces. Ligament rupture or avulsion fracture that affects the stability of the joint needs to be repaired by surgical restoration, so as not to cause repeated sprains.