Leg swelling is a common problem that can affect one or both legs. It may be isolated to the foot and and ankles or involve the entire lower leg and sometimes even the thigh. Understanding why leg swelling may occur and what causes is important in order to treat it accordinhly. It is important to note that leg swelling is a symptom of some underlying disease or disorder. Until the disease or disorder is appropriately treated, the swelling will never subside permanently.
How do the legs swell?
It is not always easy to spot a swollen leg, ankle or foot. Sometimes the swelling is so subtle that a person may not notice it. However, once it is significant the swelling is easily visible to even the untrained eye and may be pronounced when compared to the other leg that is not swollen. The reason for the swelling is that fluid accumulates in the leg. This may occur for a number of different reasons but it is usually an accuulation of tissue fluid and sometimes an accumulation of blood
Fluid and Blood
Arteries carry blood to the leg that is rich in oxygen and nutrients. Fluid seeps out of the arteries thereby transporting the oxygen and nutrients to the cells of the leg. The blood cells remain in the arteries. Tissue fluid with carbon dioxide and wastes enter the veins and are carried back to the heart. However, if too much of fluid leaks out of the arteries into the tissue spaces or if fluid is not properly drained out of the tissue spaces into the veins, it will accumulate in the leg. As a result the leg will swell.
Any additional fluid in the tissue spaces that does not enter the vein is carried away by the lymphatic vessels. This fluid is also known as lymphatic fluid. The lymphatic vessels eventually pass the lymph into the blood stream. When lymphatic fluid accumulates in any area to cause swelling, then it is known as lymphedema. Sometimes blood may leak out of the arteries and into the tissue spaces or remain in the leg veins which are engorged. This can also result in leg swelling.
Pitting vs Non-Pitting Edema
The proper medical term for swelling is edema. It is important to understand two types of edema – pitting and non-pitting. In pitting edema, pressure that is applied on the swollen leg will cause a depression for a period of time and gradually ease. This occurs when fluid accumulates in the tissue spaces. In non-pitting edema the pressure applied to the swollen leg will not cause a lasting depression when the pressure is removed. This is more likely to occur when the cells become swollen from the accumulation of fluid within it.
Causes of Swollen Legs
Some of the more common causes of leg swelling has been discussed below. It is important to understand that leg swelling is a symptom of some underlying problem. Therefore it is difficult to diagnose the cause of leg swelling without considering various other factors such as a person’s age, medical history and so on. Other symptoms such as leg pain, changes in the skin color, loss of hair on the legs and impaired movement may also provide an indication to the possible cause of leg swelling.
Read more on leg pain.
Prolonged Standing or Sitting
The muscles around the veins of the leg, both in the foot and lower leg, play an important role in pushing blood up the veins back to the heart. Therefore when these muscles are not contracting and relaxing often enough, blood drainage from the legs is slowed down. It is more commonly seen in people who sit or stand for long hours without walking around. Most people may not noticed this type of leg swelling until they have to sit for long period like when traveling on a plane.
Any injury to the leg can lead to inflammation and then swelling. The degree of swelling depends on the severity of the injury. The swelling may be localized to the site of the trauma or can affect the entire leg. With fractures, the swelling is severe and extensive especially if there is a compound fracture. However, with less serious injuries like a strained muscle or even torn muscle the inflammation is less severe and mainly in and around the site of the injury.
An infection of the leg is one of the common acute causes of leg swelling. Most of the time these localized infections are due to bacteria. It can either reach the leg through the bloodstream from some site in the body but a more common route is directly into the tissue through a skin injury. This causes inflammation at the site of the injury but may extend to other parts of the leg as the infection spreads. Cellulitis is one common and serious cause of a swollen leg.
Venous insufficiency simple means that the veins are not able to return the blood from the leg to the heart. It can affect the deep veins as is seen in deep vein thrombosis (DVT) where a clot forms in the deep leg veins. It can also affect the superficial veins as is seen in varicose veins where the vein valves malfunction and blood cannot be efficiently returned to the torso. In these cases the blood remains pooled in the veins, tissue fluid cannot be drained away and some of the fluid within the veins starts to seep out back into the tissue spaces.
Effective circulation throughout the body is not just dependent on arteries and veins. The heart is the pump that facilitates blood circulation. Therefore when the heart is failing for any reason, swelling may occur. Leg swelling is a typical sign of heart failure. Since the heart is not working as effectively, blood cannot return to it as efficiently. The blood pools at distant sites, especially in the legs. Heart failure may be due to various causes including a heart attack, enlargement of the heart, weakening of the heart muscle, heart valve disease and heart infections.
The kidneys play an important role in regulating the fluid volume within the body and controlling blood pressure. It has a direct effect on various organs, particularly the heart. When the kidneys malfunction, it may not pass out sufficient fluid from the body or be able to control the electrolyte levels. Fluid can then accumulate in the body and pool in areas like the leg. This is more likely to occur with acute or chronic kidney failure but may also be seen with kidney stones, diabetic nephropathy (diabetes kidney disease), infections and impaired blood flow to the kidney.
- Liver disease or liver failure
- Certain medication
- Rheumatoid arthritis