Venous valves are located in the veins of the upper and lower extremities of the body, including deep and superficial veins, but their location and number are not fixed, for example, there are usually 6-8 valves in the deep veins of the lower extremities, while some venous valves are relatively fixed in position, the saphenous valve at the intersection of the saphenous vein and the femoral vein, and the first venous valve about 1 cm below it, both of which are fixed in relative position. These valves are composed of two half-moon shaped folds, and their main function is to prevent regurgitation of blood from the distal limb back to the heart, so that disruption of the valves can lead to varicose veins and edema.