Pain in the side of the left foot may be due to trauma, secondary osteophytes, soft tissue contusions and so on. 1. Trauma: direct or indirect external force, causing fracture, can lead to pain and swelling of the side of the left foot. 2. Secondary osteophytes: mostly secondary to trauma, inflammation, strain injury, etc., the joint edge of the bone proliferation, will cause joint swelling, pain, can be manifested as the left foot side pain, serious cases may have limited movement, joint deformity and other manifestations. 3. Soft tissue contusion: prolonged walking or wrong left foot force can cause contusion of muscles, ligaments and tendons on the side of the left foot, causing pain. There may be other reasons for pain in the side of the left foot, such as wearing inappropriate shoes and pain caused by foot wear. It is recommended to go to the hospital in time, complete the examination to clarify the cause of the disease, and then give targeted treatment or treatment.