Following an acute injury, approximately 20-40% of patients will experience prolonged and recurrent ankle weakness and sprain, especially when walking on uneven ground, and patients often feel a loss of control of the ankle joint and inversion occurs. The sprain may or may not be accompanied by painful swelling. Some patients may feel stiffness in the ankle joint. At this point, the patient enters the chronic instability phase. The patient may have either mechanical instability or functional instability. The former means that the patient has symptoms of instability while the ankle joint mobility exceeds the normal physiological range; the latter means that the ankle joint mobility does not exceed the normal physiological range, but for a long time after the injury, the ankle joint often becomes tender and is prone to repeated sprains when walking on uneven roads. In functional ankle instability, the patient’s subjective control over the ankle joint is reduced, but the ankle mobility does not exceed the normal physiological range. In chronic lateral instability, that is, the instability may be mechanical or functional. Lateral ankle ligament rupture and laxity is the main cause of mechanical instability. Functional instability, on the other hand, is related to many factors. For example, damage to the receptor nerve fibers in the joint capsule and ligaments leads to proprioceptive impairment, resulting in decreased motor and reflex control and weakness of the ankle joint. Other factors such as peroneal muscle weakness and instability of the subtalar joint are also common causes. Repeated sprains should not be taken lightly (the above MRI image shows repeated ankle sprains causing talar exfoliative osteochondritis) and if left unchecked may lead to severe osteoarthritis. Treatment 1. Non-surgical treatment The treatment of functional instability mainly consists of rehabilitation exercises such as peroneal muscle strength training, Achilles tendon pulling, ankle balance board and balance plate exercises. The duration of training should be no less than 10 weeks. In addition, external fixation with bandages and braces can reduce ankle hypermobility and increase the sense of ankle stability. However, Rarick reported that the use of adhesive tape fixation reduced the strength by 50% after 10 minutes of activity, and Freman reported that after functional rehabilitation training, 70-85% of functional instability could obtain good results. 2.Surgical treatment For patients with mechanical instability, functional rehabilitation should be carried out first, and if non-surgical treatment fails, surgical treatment can be considered. Surgical methods can be divided into two categories: (1) anatomical repair methods. The ruptured anterior talofibular ligament and heel-fibular ligament are directly sutured or sutured to the external ankle bone to treat lateral ankle ligament injuries. When direct repair is difficult, non-anatomic reconstruction methods can be used. (2) Non-anatomic reconstruction method. According to the different reconstruction materials used, they are further divided into 3 categories: 1. using peroneal tendon 2.Use of metatarsal tendon, partial Achilles tendon or autologous free material graft. 3. Using alternative materials such as carbon fiber, bovine collagen, etc. After reconstruction, the tendon alignment conforms to the anatomical alignment of the original ligament, i.e., the anterior talofibular ligament is reconstructed and the heel-fibular ligament is reconstructed, which is a more ideal non-anatomical reconstruction method.