One lies immediately beneath the popliteal fascia, near the terminal part of the small saphenous vein, and drains the region from which this vein derives its tributaries, such as superficial regions of the posterolateral aspect of the leg and the plantar aspect of the foot.

[2] The efferents of the popliteal lymph nodes pass almost entirely alongside the femoral vessels to the deep inguinal lymph nodes, but a few may accompany the great saphenous vein, and end in the glands of the superficial subinguinal group.

The flow of lymph from the legs towards the heart is the result of the calf pump– during walking the calf muscle contracts, squeezing lymph out of the leg via the lymphatic vessels.

When the muscle relaxes, valves in the vessels shut preventing the fluid from returning to the lower extremities.

[3] This article incorporates text in the public domain from page 701 of the 20th edition of Gray's Anatomy (1918)