Pain in the medial side of the left foot is commonly caused by sprain of the left foot and paravalvular bone, as follows: First, sprain of the left foot: it can lead to significant swelling of the medial soft tissue, accompanied by pain and limited activity, and the patient usually cannot walk with weight or exercise, and the pain is more severe when pressed. Second, the paracarpal bone: the second ossification center of the foot navicular bone can produce paracarpal bone, thus causing significant protrusion of the medial side of the left foot, with local pressure and painful symptoms, accompanied by limited movement of the foot, unable to participate in strenuous sports. At this time, external spraying of analgesic and active tincture or hot compressing treatment will mostly make the symptoms significantly relieved. Therefore, if a patient has pain in the medial side of the left foot, he or she should choose the appropriate treatment according to the cause of the pain in order to quickly relieve the symptoms. In addition, patients should pay attention to the protection of the ankle joint and soft tissues of the foot to avoid injury, and surgery should be considered when the symptoms of the foot navicular are more serious.