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An important part of the body’s immune system, the lymphatic system is a series of specialized organs and vessels designed to aid in the balance of fluids within the body. Lymph nodes, the main organs of the lymphatic system, are small and egg-shaped, and are widely distributed throughout the body. The popliteal lymph nodes, for example, are located in the back of the knee in the area called the "popliteal fossa," the shallow hollow on the posterior leg.
In addition to stabilizing fluids, lymph nodes also play an essential role in trapping and filtering out foreign substances and waste byproducts that may be detrimental to the body’s overall well being. An excess of interstitial fluids, or too much fluid inside tissues from an inflammatory process due to an injury, is removed from the activity of the lymphatic system. This system also plays an important role in transporting white blood cells into the bones, a key component of the body’s ability to ward off infection.
There are between six and seven popliteal lymph nodes situated inside the fatty tissue behind each knee in the area also referred to as the knee pit. Located in key places near essential blood vessels, such as at the end of the small saphenous vein, the blood vessel near the surface of the posterior knee responsible for returning deoxygenated blood back towards the heart, these nodes aid in maintaining fluid homeostasis or balance by draining the surrounding areas of extra fluid to prevent a buildup. The popliteal artery, the blood vessel responsible for supplying blood and nutrients to the knee, thigh and calf, is another essential area where a nodes is located.
When the body is attempting to fight off an infection process, it is not uncommon to develop swelling of the lymph nodes. Called "lymphadenitis," this condition causes not only a swelling of the nodes but also a tenderness or mild pain. Swelling of the popliteal lymph nodes, however, is less common than swelling of the nodes in the neck since respiratory infections are more common than infections of the knee.
An important part of relieving lymph node swelling is to diagnose and treat the underlying problem. An infection or swelling process affecting the popliteal lymph nodes can be alleviated through the use of conservative methods such as anti-inflammatory medications, rest, and elevation of the leg. In severe cases, the use of an antibiotic may be necessary to aid the body in fighting the infection process. In the rare instances when the nodes are enlarged or inflamed due to cancer, appropriate care of the removal of the cancerous cells will help relieve the discomfort and swelling.