The main causes of left ankle swelling are considered to be related to left ankle trauma, joint inflammation, local tumor growth or lower extremity vascular disease. 1. Left ankle trauma: If the left ankle is sprained or squeezed, it may directly lead to the increase of subcutaneous exudate, thus producing the symptoms of left ankle swelling. 2. Joint inflammation: If there is inflammation in the left ankle joint, such as gouty arthritis, osteoarthritis, or rheumatoid arthritis, etc., the stimulation of inflammation will easily lead to the increase of arthritic exudate, which will result in the swelling of the left ankle. 3. Local tumor growth: in the position of left ankle, if there is local tumor growth, such as bone tumor, it is possible to produce the occupying effect, thus forming the symptom of swelling. 4. Lower limb vascular disease: If varicose veins or venous thrombosis occur in the left lower limb, it may directly affect the blood return, thus producing the symptom of left ankle swelling. If the swelling of the left ankle lasts for a long time, you need to check the cause of the disease, exclude gout, heart failure and kidney failure and other diseases, and then carry out targeted treatment under the guidance of professional physicians.