The formation of thrombosis in the veins of the lower limbs is called lower limb vein thrombosis. Lower extremity vein thrombosis is divided into superficial vein thrombosis and deep vein thrombosis. Superficial vein thrombosis is formed in the varicose veins on the basis of saphenous vein, which is the superficial vein thrombosis. Deep vein thrombosis is due to venous valves, venous reflux disorders, high viscosity of blood or damage to the veins where blood coalesces to form deep vein thrombosis in the lower extremities. Superficial vein thrombosis and deep vein thrombosis are treated differently. If superficial vein thrombosis is not treated, the thrombus will gradually become larger and enter the deep vein, forming a deep vein thrombosis. It is more difficult to treat, so early treatment is necessary if thrombosis is found.