A common complaint that affects many people is varicose veins, which are caused by the superficial veins of the leg not working as well as they could. However, DVT is different from varicose veins and is a more serious problem. There are two systems of veins in your legs: deep veins, which are the most important and carry most of the blood back to your heart, and superficial veins just under the skin, which are less important and transport blood from the skin and from the tissue just below the skin. Varisoce veins are superficial veins that have become enlarged, and blood can pool there, especially on standing. A clot can form in varicose veins, but this is called superficial thrombophlebitis. It does not usually cause any problems other than local pain and inflammation - but very rarely it can lead to a clot forming in one of the deep veins (i.e. a DVT).