The lymph nodes in the leg are located in the pit area behind the knee known as the popliteal fossa. These nodes are called the popliteal lymph nodes, according to the National Center for Biotechnology Information.
The popliteal nodes can be divided into two groups, superficial and deep, as detailed in Basic Human Anatomy. The superficial popliteal nodes are located near the end of the saphenous vein, and the deep popliteal nodes are located near the popliteal vessels. The term "popliteal" dates back to the 18th century and is derived from a Latin word meaning the hollow of the knee, according to OxfordDictionaries.com.