Popliteal Lymph nodes
Popliteal fossa is a space present behind the knee, it is diamond in shape with semimembranosus and semitendinosus forming the superomedial boundary while biceps femoris is on the superolateral side. Lower boundaries of this space is bounded by heads of gastrocnemius. Popliteal lymph nodes is one of the few contents of this fossa and are embedded in the fat of the space. In this article we will discuss the gross and functional anatomy of the popliteal lymph nodes. We will also discuss the clinical relevance of the structure, and provide a summary of key points at the end of the article. We will finally conclude with some review questions to test the reader’s understanding of the article content.
The popliteal lymph nodes are found in the popliteal fossa alongside the other contents. The popliteal artery is deepest, the vein lies slightly more superficial but is usually tightly adhered to the artery, tibial and common fibular nerves as the sciatic nerve (ventral rami of L4-S3) divide well above the popliteal fossa. The tibial nerve innervates all the muscles of the posterior compartment of the thigh (aside from the short head of biceps femoris, which is innervated by the common fibular nerve).
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- Semitendinosus (medial border)
- Semimembranosus (medial border)
- Popliteal Artery (deepest structure)
- Popliteal Vein (superficial to the artery)
- Tibial and common fibular Nerves (most superficial structures in the popliteal fossa)
- Biceps femoris (Lateral border)
- Gastrocnemius two heads (inferior border)
The popliteal lymph nodes are relatively small in size. There are usually approximately 6 to 7 popliteal lymph nodes and they are embedded in the popliteal fat. One lies at the point where the short saphenous vein joins the popliteal vein. It can be found just deep to the popliteal fascia and drains the saphenous vein territory e.g. the superficial regions of the lateral leg and the sole of the foot. A second node lies between the popliteal artery and the dorsal aspect of the knee joint. This receives lymphatic vessels from the knee joint. The remainder of the lymph nodes lie around the popliteal vessels, and receive lymphatic fluid from the trunks that accompany the anterior tibial, posterior tibial and fibular arteries.
The vast majority of the efferent from the popliteal lymph nodes pass along the femoral vessels in order to reach the deep inguinal of lymph nodes. A few of the popliteal lymph nodes accompany the greater saphenous vein, and therefore drain into the superficial inguinal group of lymph nodes. The movement of lymphatic fluid from the legs, to the knee and up to the femoral group in the femoral triangle, is assisted by muscular contractions from the musculature of the leg. The valves within the lymphatic vessels also prevent backflow of fluid. This system mirrors that of the venous circulation of the lower limb.