The common causes of swollen ankles are soft tissue injury, varicose veins of the lower limbs, cardiac insufficiency and so on. 1. Soft tissue injury: soft tissue injury can be caused by trauma, long-term exertion of the feet, catching cold and so on, which causes ankle swelling. 2. Varicose veins of the lower limbs: severe varicose veins lead to tortuous, piling up and deformation of blood vessels, affecting venous return and ankle swelling. 3. Cardiac insufficiency: it leads to blood circulation obstacle. Ankle is located in the lower end of human body, blood is easily stagnated in the lower limbs, thus ankle swelling occurs. There may be other reasons such as renal insufficiency and gout, etc. It is recommended to go to the hospital in time, improve the examination to clarify the cause of the disease, and carry out standardized treatment under the guidance of the doctor.