Varicose veins are veins that have become enlarge and twisted. Carl Arnold Ruge is credited with having first defined varicose veins as "any dilated, elongated and tortuous vein irrespective of size". The term commonly refers to the veins on the leg, although varicose veins occur elsewhere. Veins have leaflet valves to prevent blood from flowing backwards (retrograde). Leg muscles pump the veins to return blood to the heart. When veins become enlarged, the leaflets of the valves no longer meet properly, and the valves don't work. One cause of valve failure is deep vein thrombosis (DVT), which can cause permanent damage to the valves. The blood collects in the veins and they enlarge even more. Varicose veins are common in the superficial veins of the legs, which are subject to high pressure when standing. Besides cosmetic problems, varicose veins are often painful, especially when standing or walking. They often itch, and scratching them can cause ulcers. Serious complications are rare. Non-surgical treatments include sclerotherapy, elastic stockings, elevating the legs, and exercise. The traditional surgical treatment has been vein stripping to remove the affected veins. Newer surgical treatments are less invasive (see radiofrequency ablation and Endovenous Laser Treatment) and are slowly replacing traditional surgical treatments. Since most of the blood in the legs is returned by the deep veins, and the superficial veins only return about 10%, they can be removed or ablated without serious harm. Varicose veins are distinguished from reticular veins (blue veins) and telangiectasias (spider veins) which also involve valvular insufficiency, by the size and location of the veins.