Sudden swelling of the ankle of the elderly may be caused by physiological phenomena such as overwork, varicose veins of the lower extremities, nephrotic syndrome and so on. 1. Physiological phenomenon: the elderly usually have poor physical strength, when the patient walks or works excessively for a long time, it may cause fatigue injury to the soft tissues of the neck of the foot, and at the same time, it will produce a large amount of lactic acid, and there is a viscous buildup, which will make the patient’s feet and neck appear to be swollen. 2.Pathological factors (1) Varicose veins of the lower limbs: When varicose veins of the lower limbs occur, blood circulation in the lower limbs of patients may be blocked, resulting in venous blood backflow downward, leading to the accumulation of blood in the neck of the foot and the dorsum of the foot, which leads to the symptom of sudden swelling of the neck of the foot. (2) Nephrotic syndrome: patients with nephrotic syndrome are usually accompanied by hypoproteinemia, which leads to a decrease in the plasma colloid osmotic pressure, resulting in the rapid penetration of intravascular water into the blood vessels outside the blood vessels, and the intravascular water to the outside of the blood vessels will reach the sagging part of the human body, which will lead to the symptoms of swelling of the neck of the feet. Sudden swelling of the neck of the feet of the elderly may also have other reasons, it is recommended that the patient timely consultation and examination, to clarify the specific cause of the disease, and then follow the doctor’s instructions for treatment.