Varicose veins are usually bulging, bluish cords running just beneath the surface of your skin. They almost always affect legs and feet. Visible swollen and twisted veins -- sometimes surrounded by patches of flooded capillaries known as spider veins -- are considered superficial varicose veins. Although they can be painful and disfiguring, they are usually harmless. When inflamed, they become tender to the touch and can hinder circulation to the point of causing swollen ankles, itchy skin, and aching in the affected limb.

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Besides a surface network of veins, your legs have an interior, or deep, venous network. On rare occasions, an interior leg vein becomes varicose. Such deep varicose veins are usually not visible, but they can cause swelling or aching throughout the leg and may be sites where blood clots can form.

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Varicose veins are a relatively common condition, and for many people they are a family trait. Women are at least twice as likely as men to develop them. In the U.S. alone, they affect about 23% of adult Americans.

Source: Webmd.com