To best understand varicose veins you need to know a little about the circulatory system in general.

The heart is the central pump that forces oxygenated blood via arteries and capillaries to nourish every tissue and cell throughout the body. Arteries are the thick walled vessels that carry blood from the heart to the periphery. Veins are thin walled vessels that carry blood from the tissues back to the heart and lungs to be re-oxygenated and start the cycle over again.

There are three important types of veins at work in your legs. The deep veins are large in diameter and are situated deep within the muscle close to the bone. The veins of the deep system carry the majority of blood from your legs back to your heart. Superficial veins lie within the fatty tissue above the muscles, and are sometimes visible through the Skin. The largest and longest of the superficial veins courses down the inner aspect of your thigh and lower leg. This, the Greater Saphenous Vein, is connected to the deep vein system via the femoral vein up in the groin. The other main superficial vein, the Short Saphenous Vein aka Small Saphenous Vein, begins behind the knee and runs down the back of the calf in your leg. When either of these veins becomes dilated and tortuous, they are called varicose veins. Perforator veins are short connecting veins between the deep and superficial veins.

Your leg veins may hold as much as 70% of your total blood volume at any given time.

How does blood get back from the periphery to the heart?

Blood moves through the venous system mainly by contraction of muscles in your calves and feet. As these muscles contract, they compress the veins in your leg, propelling de-oxygenated blood back toward your heart and lungs. Veins in your legs have tiny one-way valves that float open as blood flows toward your heart, and then close to prevent the blood from flowing backward toward your feet (reflux). If these valves are damaged or defective, reflux occurs. This means that blood flows the wrong way down the vein. This is the cause of venous hypertension (high blood pressure in the veins) and the fundamental cause of all the problems associated with varicose veins or chronic venous insufficiency.