After an acute injury, approximately 20-40% of patients will experience long-term recurrent ankle weakness and sprains, especially when walking on uneven surfaces, and the patient will often feel a loss of control of the ankle joint and inversion. 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. In the former case, the patient has symptoms of instability and the ankle joint mobility exceeds the normal physiological range; in the latter case, the ankle joint mobility does not exceed the normal physiological range, but the ankle joint often becomes tender for a long time after the injury and is easily sprained when walking on an uneven road. In functional ankle instability, the patient’s subjective control over the ankle joint is reduced, but the ankle joint mobility does not exceed the normal physiological range. In chronic lateral instability, the instability may be both mechanical and functional. Lateral ankle ligament rupture and laxity is the main cause of mechanical instability. Functional instability is related to a number of 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. Treatment of repeated ankle sprains 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 training time should be not less than 10 weeks. In addition, external fixation with bandages and braces can reduce ankle hypermobility and increase ankle stability. However, Rarick reported that the strength of the ankle can be reduced by 50% after 10 minutes of activity by using adhesive tape, and Freman reported that 70%-85% of functional instability can be achieved after functional rehabilitation training. 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.