1. Causes and principles of ankle sprain. According to the anatomical characteristics, the ankle joint is composed of the joint surface under the tibia and fibula and the joint surface of the upper part of the talus (talar talus slide). The flexor muscles of the foot are stronger than the extensor muscles, and the inversion muscles are stronger than the extensor muscles; plus the external ankle is longer than the internal ankle, and the internal ankle triangular ligament is stronger than the three external ligaments. Therefore, the range of motion of the inversion is greater than that of the valgus. In addition, the talus body is wide at the front and narrow at the back. When the foot is dorsally extended, the talus enters the ankle point completely and the ankle joint is stable and not easily sprained, while when plantarflexed, the narrow part at the back of the talus enters the wide part in front of the ankle point and the ankle joint is relatively unstable and easily sprained. The technology of ball sports is complex, and the conversion of technical movements in practice is frequent, requiring constant change of direction, emergency stop and start, especially in basketball, basketball, volleyball, jumping up and dunking, when students leave the ground in the air stage, their feet are in plantar flexion and inversion, if the body weight is unstable when landing, tilting to one side or stepping on other people’s feet and balls, or on the uneven ground, and the students Lack of self-protection strain, will land on the front and outside of the foot, so that the foot inversion, resulting in injury. 2. Symptoms. After the injury, there is obvious pressure pain on the medial or lateral side of the ankle joint; there is obvious swelling on the inner and outer ankle, localized subcutaneous bruising, limited ankle movement and difficulty in walking. 3. Field treatment of ankle sprain. Immediately after the injury, give cold compress, pressure bandage, elevate the affected limb, fix rest, and apply new wound medicine externally. After 3 days, massage: (1) massage the Xiexi point (the center of the transverse line of the ankle joint on the back of the foot, between the long thumb tendon and the long toe tendon) for 1 min; (2) massage the Kunlun point (the midpoint of the line between the outer ankle and the Achilles tendon) for 1 min; (3) massage the Hanging Bell point (3 inches below the tip of the outer ankle, the posterior edge of the fibula) for 1 min; (4) massage the Yanglingquan point (the depression below the small head of the fibula) for 1 min. All of the above points should be massaged to the extent that the patient feels soreness and swelling. 5.Post-injury exercises. After the pain and swelling is reduced, that should be in the sticky plaster support belt fixed under the ground walking or walking with crutches, 1 to 2 weeks later can be muscle strength and coordination exercises, jogging on the sand or walking or jumping exercises on the bumpy slope, and gradually into formal exercises. 6.Strengthen preventive measures. An important reason for the injury is the lack of self-protection awareness, do not pay attention to preventive measures. Therefore, we should fully prepare for the activities, improve the venue facilities, cultivate and improve self-protection ability, improve the muscle strength of the ankle joint, as well as the stability and coordination of the ankle joint, and wear a good protective support belt when practicing.