Your leg veins are organised into two distinct networks, and each has a different job. Knowing the difference helps make sense of why some vein problems are unsightly, some cause skin and swelling problems while others can be life-threatening.

The superficial veins lie just beneath the skin, in the fatty layer between the skin and the muscle. They carry about 10% of the blood up your leg. These the veins that you can see and feel through the skin. There is a pattern to these veins as well including the great saphenous vein (GSV) that runs up the inner leg from the ankle to the groin and is the longest vein in your body. The small saphenous vein (SSV) runs up the back of the calf to behind the knee or thigh. Lots of smaller veins drain into these main superficial veins. These superficial or skin veins are the veins that can develop into varicose veins when their valves become faulty. If left untreated overtime the constant blood-back pressure can cause other problems as well.

The deep veins run inside the muscles of the leg, closer to the bone. They carry most of your blood, about 90%, back to your heart. The main deep veins include the femoral vein in the thigh, the popliteal vein behind the knee and 2-3 deep veins below the knee. Because they sit deep within the leg, you cannot see them from the outside. Deep vein problems are less common that the superficial vein problems, however, are the more serious ones. If you develop a clot or blockage (deep vein thrombosis, or DVT) in these veins these blood clot can travel to the lungs.

The two systems are connected in two ways. Along the length of your legs there are short vessels called perforator veins, which connect the superficial and deep veins at various points along their way up your leg. One-way valves in the perforators veins allow blood to move from the superficial system into the deep system, but not the other way. When these valves fail, high-pressure blood from the deep veins can be pushed into the superficial veins, creating or adding to the problem of varicose veins. The other way the deep and superficial veins join is where the GSV dives down to join the femoral vein, just below the groin crease, before it travels up into your abdomen. The SSV behind the knee or thigh also dives down to join the popliteal or femoral vein as it travels up through your thigh muscles.

At our Woolloomooloo Vein clinic in Sydney’s inner Eastern suburbs, we have Vein Surgeons and specialist vein sonographers that can investigate, diagnose and treat all your vein problems, including DVTs, varicose veins and when your perforator veins start bleeding or causing varicose veins.