Varicose veins are abnormal swollen tortuous veins that develop beneath the skin. These unwanted blood vessels may be raised in a rope-like manner above the skin surface and have a red or bluish color. They appear often on the thighs, around the knees, the calves, and around the ankle.

The veins are responsible for returning the blood to the heart. In the leg veins, the blood must go upward against gravity. During walking the calf muscles contract and pump the blood upward towards the heart. Veins have one way valves that prevent blood from flowing back towards the feet.
Varicose veins develop when these valves do not function properly or when the vein wall weakens. Gravity forces blood to leak down and collect in the superficial veins. These veins respond by enlarging and twisting and become visible as varicose veins. These veins are abnormal, do not transport blood back to the heart efficiently, and are not necessary to the circulatory system. If their presence is distressing, they can be removed without bad effects.