Lower extremity venous thrombosis clinically refers to deep vein thrombosis of the lower extremities, and its symptoms are diverse. Most patients present with swelling and edema of the lower extremities, in addition to pain, erythema, fever, superficial venous dilatation, pain in the lower leg during foot dorsiflexion, and cyanosis of the swollen lower extremities. The central type refers to the thrombosis of the common iliac vein to the femoral vein, and the peripheral type refers to the thrombosis of the femoral vein or the deep venous plexus of the calf muscle. Central type: The whole lower extremity is obviously swollen, and the root of the diseased side of the thigh (iliac fossa and femoral triangle) is painful and painful, the superficial veins are dilated, and the skin temperature of the diseased side of the thigh is elevated, with more onset on the left side than on the right side. Peripheral type: Thrombosis confined to the femoral vein is characterized mainly by painful swelling of the thigh and not severe swelling of the lower extremity. In deep vein thrombosis confined to the calf, there is sudden onset of severe pain in the calf, and the affected foot is unable to land on the ground and the symptoms are aggravated when walking. The lower leg is swollen and has deep pressure pain. Excessive ankle dorsiflexion test can lead to severe pain in the lower leg. Mixed type: The entire lower extremity is significantly swollen and painful, with pressure pain in the femoral triangle, popliteal fossa, and calf, often accompanied by elevated body temperature and rapid pulse rate. If the disease continues to progress, if it is accompanied by thrombotic superficial phlebitis, the limb will be extremely swollen and the blood supply to the lower extremity arteries will be impaired by compression of the lower extremity arteries. Symptoms of arteriopathy such as loss of dorsalis pedis artery pulsation may occur. The sudden occurrence of swelling and pain in one lower limb should exclude the possibility of deep vein thrombosis in the lower limb, and the diagnosis should be confirmed in hospital in time.