Darkening of the ankles may be caused by long-term ultraviolet radiation, varicose veins of the lower extremities and arteriosclerosis occlusion of the lower extremities. 1. Long-term ultraviolet radiation: If there is no clothing to cover the ankles in summer, resulting in long-term ultraviolet radiation on the ankles, the ankles may appear blackened skin manifestations. 2. Varicose veins of the lower limbs: If there are varicose veins of the lower limbs, resulting in reduced venous return and poor blood circulation, it will gradually deepen the pigmentation of the ankles and darken the skin. 3. Arteriosclerosis occlusion of the lower limbs: If you suffer from arteriosclerosis of the lower limbs, it may cause serious ischemia and lack of oxygen in the muscle tissues at the ankles due to the obstacle of blood supply, thus leading to the phenomenon of darkening of the skin of the ankles. Black ankles, it is recommended to go to the hospital in time for examination and treatment.