The great saphenous vein (GSV), previously referred to as the long saphenous vein, is a superficial leg vein that runs from the top of the thigh near the groin, down the inner thigh all the way to the inner ankle. The top blue arrow in this diagram points to the location of the great saphenous vein. In people presenting with varicose veins, the Great Saphenous vein is responsible for varicose veins over 80% of the time. Varicose veins originating off the GSV typically appear in the inner thigh, inner calf, across the shin, or start in the thigh and run along the back of the calf. The other superficial vein largely responsible for varicose veins in the small saphenous vein. The small saphenous vein (SSV) runs along the back of the calf. Varicose veins on the backside of the leg are often caused by leaky valves within the small saphenous vein.