It is estimated that among people aged 15 to 65, 35 to 40% of men and 40 to 45% of women have varicose veins or thread veins in the lower extremities.

There is a clear female dominance among those affected by the disorder, and also an increase in the prevalence of varicose veins with age in both sexes.

Factors contributing to poor venous flow include excess weight and pregnancy. Heredity is an important factor, the risk for the disease increasing when both parents have the condition.

If both parents are free of varicose veins, 20% of their offspring will have the condition. If only one parent has varicose veins, 25% of boys and 62% of girls will. If both parents have varicose veins, 90% of the children also will.

The geographic location is also a factor. The areas most affected are: Europe, North America and South Eastern America. The least affected areas are Black Africa, New Guinea and India.

Civilisation and lifestyle rather than race seem to be a factor in venous circulation. In Black Africa, varicose veins are 20 to 100 times less frequent than in France. In the United States, blacks have as many varicose veins as whites with similar incomes. In India, varicose veins are rare except in cities, where 25% of the population is affected.

How does venous circulation work?
The role of the venous system of the lower extremities is to make sure blood flows back to the heart, whatever the position of the body, whether resting or moving. It also acts as a reservoir for the blood mass, as well as a regulator for the cardiac output and body temperature. In order to achieve this, there are:

Two different venous systems and a valve system

The venous systems

The deep venous system drains 95% of the blood flow returning to the heart, protected and surrounded by muscles and envelopes a good portion of the way. The venous system is made of calf veins called sural veins, thigh veins called femoral and popliteal veins, and abdominal-pelvic veins called illiac veins and inferior cave veins.
The superficial venous system, minor and with a low flow, drains only a small portion of the blood mass. It is located under the skin and inside the skin. It drains through two main collecting trunks: the internal saphenous vein which runs along the internal side of the leg and thigh, and joins the femoral vein at the inguinal fold, and the external saphenous vein which runs along the external side of the ankle toward the posterior side of the leg and joins the popliteal vein above the back of the knee.
The perforator veins: the deep venous system and the superficial venous system are connected by a network of short veins called perforators. These connecting veins bring the blood from superficial to deep areas. They are found in many places of the legs and thighs.
The valvs

The deep venous system, the superficial venous system and the perforator veins are equipped with small valves which open up when the blood flows normally from feet to heart and from outside in, then close to prevent blood reflux when it could reverse (such as when one stands up or makes certain strenuous moves).
What makes the venous system flow?

Venous circulation is more complex than arterial circulation. Contrary to arterial circulation, there is no cardiac pump to propel the venous blood, which must also fight against gravity in a standing person.

The energy needed for the good functioning of the venous circulation comes mostly from muscles. Contracting muscles (while walking for instance) compress (with each step) the deep veins, pushing their content toward the heart (the calf muscle pump).

Other minor mechanisms also come into play to push up the blood flow toward the heart:

The plantar venous sole is squeezed with each step like a sponge, which causes a rapid evacuation of the blood inside
The diaphragmatic venous pump accelerates the return of the peripheral venous blood up toward the heart with each inhalation as the diaphragm moves down.
When lying, the blood flows very easily in the veins as it no longer has to fight gravity.

If the risk factors or contributing factors are now well known, the real cause of venous dysfunction in the lower extremities still remains a mystery.

How does the venous system work in a person with varicose veins?
The exact mechanism of varicose veins formation is still poorly understood and is complex.

In its normal state, the vein wall displays a significant distensibility.

Varicose veins can occur when there is:
- An excessive distensibility occurring without any obvious reason
- A change in the functioning of the internal valves
- A decrease in the muscular tone in case of weak leg muscles
- A decrease in the efficiency of the diaphragmatic pump in a person with breathing problems

Poor quality of the plantar venous sole when the feet are either too arched or too flat.

When the veins are enlarged, the internal valves become unable to close completely as the blood tries to flow back toward the feet. Due to excessive pressure, this phenomenon exacerbates the enlargement of the underlying vein walls.

This leads to a clash between the blood flow trying to move toward the heart and an opposite flow moving toward the lower extremities. The resulting pressure increase is felt not only on the main axes (saphenous veins) but also on the tributaries and eventually on the whole superficial venous system.

The blood stagnating in enlarged veins that can no longer play their role causes the cutaneous and surrounding subcutaneous tissues to fill with fluids. This swelling is responsible not only for the feeling of heaviness in the legs, cramps and discomfort, but also oedemas and skin complications such as eczema, pigmentation, thickening of the skin and, eventually, ulcers.

In extreme cases, when varicose veins are very large and the blood flow markedly reduced, superficial phlebitis may appear due to the formation of blood clots inside the varicose veins.

too flat

too arched