The femoral artery is a very important large artery in the leg. If there is a thrombosis in the femoral artery, it can cause numbness and coldness in the leg, pain, low skin temperature, and terminal cyanotic manifestations. In case of acute ischemia, this symptom is very serious. If a thrombus is present in the femoral vein, or in the popliteal vein, it can cause swelling and pain in the leg. If the thrombus is dislodged, it will enter the pulmonary artery along the blood flow and cause pulmonary embolism, which is characterized by difficulty in breathing, chest pain and hemoptysis. Therefore, if there is a thrombosis in the leg, it is necessary to distinguish whether it is an arterial thrombosis or a venous thrombosis, which will cause different symptoms and different treatment.