Veins are thin-walled blood vessels which return blood to the heart. They contain a system of valves to keep blood flowing in the right direction.
There are two separate networks of veins in the leg which are divided into a superficial and deep system. These two systems are inter-connected at the groin and behind the knee.
Varicose veins occur when there is weakness in the wall of the vein or damage to the valves. This results in an increased pressure inside the vein causing dilatation.
Risk factors include increasing age, pregnancy and previous deep vein thrombosis.
Over 25% of women and 10% of men will be affected by varicose veins at some point in their lives. Some will seek treatment due to the unsightly appearance but varicose veins can also cause significant discomfort in many patients.