Depression on the inner side of the ankle is usually caused by edema. Causes of inner side of the ankle edema include kidney function abnormality, right heart failure, lower extremity venous thrombosis and so on. 1. Abnormal renal function: the root cause of abnormal renal function is renal fibrosis, which can be manifested as various renal diseases, such as renal failure, nephrotic syndrome, renal insufficiency, renal cyst, nephritis, uremia and so on. In the early stage, there may not be any signs, and then with the gradual development of the disease, there are different degrees of edema and other symptoms. 2. Right heart failure: a complex clinical syndrome that occurs when the systolic and diastolic dysfunction of the right heart leads to insufficient cardiac output to meet the body’s demand or fails to develop normal filling pressure. Common symptoms include loss of appetite, abdominal distension, nausea, vomiting, renal hypoplasia, edema, etc., in which edema is mostly seen in the lower limbs first. 3. Lower extremity venous thrombosis: it is a kind of non-septic inflammation occurring in the veins of the lower extremity, accompanied by secondary thrombosis in the lumen of the blood vessel, which mainly involves the superficial veins or deep veins of the lower extremity. Its clinical characteristics are swelling and pain in the affected limbs, aggravated by activities, and subcutaneous striae with tenderness can be detected. When the symptoms of depression appear on the inner side of the ankle, it is recommended to consult a doctor in time to clarify the cause of the disease and then treat the symptoms, so as not to worsen the condition.