What causes swelling in the legs from the knee down

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Swelling of the foot and/or leg can have a number of causes. If both legs are affected it may suggest a more generalised cause such as fluid retention in the body. Kidney, liver and heart function can influence this. It may also be a side effect of medications. A long period of immobility with the legs dependent (below heart level) can lead to a build up of fluid, since we rely on the movement of the muscles in the leg to move the blood and fluid up out of the legs towards the heart. In some illnesses the protein level in the blood stream drops and this causes fluid to move out into the tissues causing bilateral limb swelling. In some cases abnormal fat distribution leads to the appearance of limb swelling and it is mistaken for fluid.

When one limb is affected it can point to a more local problem in the leg being the cause of the swelling. There are a number of possibilities :

1. Venous insufficiency - poor return of fluid in the veins from the leg. (valve failure, DVT, varicose veins)
2. Infection - tissues are inflamed and accumulate fluid which leaks from the circulation.
3. Injury - after any injury the healing repsonse involves some element of swelling
4. Lymphatic failure - damaged, blocked, or absent lymph channels and glands.

Investigations are therefore required to establish which of the above problems is causing the leg swelling. From the vascular perspective, it is important to establish the function of the veins. Lymphoedema is different from venous oedema, and it may be clear that the swelling is lymphoedema from examination. Sometimes specific tests are needed to be more certain.

Treatment

This will be directed to the underlying cause. Compression with support stockings is often helpful. Vein treatments may be useful. Difficult lymphoedema may need more specilaised therapy.

LYMPHOEDEMA

What is lymphoedema?
We all have a small amount of fluid (lymph) in our body tissues. This fluid leaves our blood system to provide water and nourishment to the tissues. Most of this fluid is collected by a system of drainage tubes, similar to blood vessels, called the lymphatic system. Lymphoedema is swelling which is due to a build up of lymph in the limbs if the fluid is not draining out properly.

To start with, the swelling is often noticeable at the end of the day and goes down at night. However, unless the swelling is treated properly, the fluid becomes fixed in the leg permanently.

What causes lymphoedema?
The most common cause for lymphoedema is that you were born without enough lymphatics. If there are very few lymphatics then the swelling may start as a teenager or even earlier. This type of lymphoedema is called Milroy's Disease. One leg is often worse than the other and sometimes only one leg is affected.

In less severe cases the lymphatics may be able to cope initially and only start to fail when you are older. This kind is sometimes called Lymphoedema Tarda.

Are there any other causes?
Lymphoedema can also be caused if the lymphatics of the arm and leg are damaged by surgery or radiotherapy for the treatment of cancer. Sometimes this is unavoidable if the cancer is to be cured. .

What are the effects of lymphoedema?
Apart from the uncomfortable and unsightly swelling, lymphoedema can cause problems, especially if it is not kept under control. There is an increased risk of infection under the skin (cellulitis) and repeated attacks of cellulitis lead to more lymphatic damage. This vicious circle may eventually lead to severe infections, ulcers and even amputation in extreme cases.

What is the treatment?
Lymphoedema cannot be cured but it can usually be controlled so that complications do not occur later. The mainstays of treatment are compression bandages or stockings, elevation of the limb and external pneumatic compression.

Elevation of the limb
Whenever the leg is elevated, fluid will tend to drain out of it. Put your legs up whenever you can and as high as you are able - the arm of a sofa is good. Elevate the end of your bed (6 inches or so) in order that your feet are a little higher than your head. You can use some old books for this.

Compression bandages or stockings
Compression is required to squeeze the fluid out of your legs when you are standing up. Bandages may be required at first, to remove the worst of the swelling, before stockings can be used. These stockings need to be specially fitted and are much stronger than ordinary "support tights". If the swelling only affects the lower leg, then you can wear a below-knee stocking that is self-supporting, like a pop-sock. The usual strength of stocking used is a Class II, but sometimes a stronger Class III is required. If you have difficulty putting on your stockings, then you can buy a special stocking applicator.

External Pneumatic Compression (EPC)
Despite compression stockings, many people find that some swelling accumulates by the end of the day. The EPC device is a pneumatic boot that inflates and deflates to squeeze fluid out of the leg. EPC is normally used in the evening to get rid of any fluid that has built up despite compression stockings. If your doctor thinks you need EPC therapy, a trial of the device will normally be arranged so that you can decide whether it is worth buying one.

What about surgery?
Many operations have been tried to cure lymphoedema, but none have been very successful. Surgery to reduce the size of the lower leg, liposuction or surgical excision (Homan's Reduction) may be suggested if your leg remains very swollen despite compression therapy.

How can I help myself?

Wear your compression stockings every day from morning to night.
Elevate your legs whenever possible.
Take plenty of exercise and don't put on weight.
Keep the skin in good condition by using plenty of moisturising cream to prevent dryness.

For more information go to The Circulation Foundation;   NHS Choices or Foldi clinic