The common causes of pain on the outside of the foot in running are physiological phenomenon, sports injury, heel bursitis, flat foot and so on. 1. Physiological phenomenon: If there is no sufficient warm-up before exercise, or the exercise is too strenuous, and there is transient synovial edema or lactic acid accumulation in the ankle joint after the exercise, ankle pain can occur, which is a normal phenomenon, and it can be relieved after resting. 2. Sports injuries: If the ankle joint is sprained due to improper posture during sports, resulting in soft tissue injuries such as muscle and tendon injuries around the ankle joint, pain may occur. 3. Post-heel bursitis: If you wear shoes that don’t fit your feet or run for too long, your heel is subjected to repeated mechanical stimulation, which triggers aseptic inflammatory reaction and can also cause pain. 4. Flat feet: due to congenital developmental abnormalities, long-term standing, etc., the arch of the foot becomes shallow or disappears, and the buffering capacity decreases, which can cause pain after running. There are more reasons for pain on the outside of the foot after running, and it may also be related to ankle fracture, fasciitis and other diseases. If the symptoms continue to be unrelieved, it is recommended to consult a doctor in time to clarify the cause of the disease and carry out targeted treatment.