All veins have “one-way” valves that assist in returning de-oxygenated blood back to the heart and lungs. When these valves function properly, venous bloodflow efficiently travels back to the heart, against the forces of gravity. In many cases, the valves of the Greater and Lesser Sapphenous Veins can, through several processes, become inefficient, allowing blood to flow back toward the feet, a condition is called Venous Reflux. When this occurs, the veins become overpressurized and become visible as varicose veins.