How do varicose veins form?

The essential defect is a weakness in the valves or walls of the veins which allows blood to flow in the wrong direction. Veins are designed to carry blood from the limb back towards the heart, upwards against gravity. This is managed by valves within the veins themselves which shut to prevent backwards flow of blood. If the valves are defective, faulty or weak then there is backwards flow which results in the formation of varicose veins.

Aggravation is also caused by pregnancy or obesity, which places additional strain on the valves. As the veins stretch under the additional pressure they tend to dilate, taking on the apperance of varicose veins.