Unexplained bruising of the ankle is usually caused by rupture of the capillaries under the ankle. If the cause is unknown, it is usually caused by abnormal coagulation function, such as thrombocytopenia or coagulation factor deficiency. In addition, if an elderly patient has been taking oral anticoagulant drugs for a long time due to coronary artery disease, commonly enteric aspirin, it may also lead to unexplained rupture of local capillaries and bleeding. However, this condition does not occur frequently and does not require special treatment.