Clinical signs and symptoms of lower extremity venous thrombosis include localized redness, swelling, pain, fever, and possibly varicose veins, concave edema, and tenderness in the area of the femoral triangle and gastrocnemius muscle. If the embolus is dislodged pulmonary embolism symptoms such as dyspnea, chest pain and hemoptysis may occur. Lower extremity venous thrombosis is an abnormal clotting of blood in the veins, blocking the venous lumen and causing obstruction of venous return. Clinically, local redness, swelling, pain, fever, varicose veins, edema, pressure pain in the femoral triangle and gastrocnemius muscle area appear due to the blood flow obstruction. In severe cases, venous thrombosis of the lower extremities affects the venous blood supply, resulting in insufficient blood supply to the corresponding extremities. If the thrombus is unfortunately dislodged, it will lead to the symptoms of the acute phase of lower extremity venous thrombosis, i.e., the thrombus enters the pulmonary circulation with the blood flow, resulting in pulmonary embolism, at which time the patient’s symptoms are respiratory difficulties, chest pain, hemoptysis. In case of lower extremity venous thrombosis, it is important to go to the hospital in time and under the guidance of the doctor, do not delay, so as not to cause life-threatening.