Venous insufficiency is a very common condition resulting from decreased blood flow from the leg veins up to the heart, with pooling of blood in the veins. Normally, one-way valves in the veins keep blood flowing toward the heart, against the force of gravity. When the valves become weak and don't close properly, they allow blood to flow backward, a condition called reflux. Veins that have lost their valve effectiveness, become elongated, rope-like, bulged, and thickened. These enlarged, swollen vessels are known as varicose veins and are a direct result of increased pressure from reflux. A common cause of varicose veins in the legs is reflux in a thigh vein called the great saphenous, which leads to pooling in the visible varicose vein below.