Varicose veins are most common in the lower extremities, because humans are upright walking animals, the venous blood in the lower extremities in the upright state has to fight gravity and flow back from the legs to the heart, in this case humans have gradually evolved venous valves. The role of the venous valve is equivalent to a one-way valve, when the blood on the legs from the bottom to the top, the valve opens, the blood due to gravity to fall down, this time the valve will close, so as to ensure that the blood is a continuous flow from the bottom to the top of the state. For people who stand for a long time or walk for a long time, the venous valve should bear very high pressure for a long time, and over time the function of the venous valve will be affected, and it will be closed incompletely, then the whole vein will bear very high venous water column pressure, and the vein will be impacted by the high pressure state, gradually tortuous, expansion, and finally form varicose veins.