When ALL of the valves are working normally, and the leg is able to move normally, the blood is pumped up both deep and superficial veins during muscles contraction - ie: PUMPING the leg.

When the leg RELAXES, the pumping stops and the blood starts to flow down both deep and superficial vein systems.

This back flow of blood causes the valves to snap shut, stopping the blood from flowing back down the leg.

This is how the leg vein pump works.

Now we will look at what happens to the leg when the valves fail.