Anatomy of the popliteal fossa

The popliteal fossa is the space behind your knee; and even though it may not look like much from the outside, it’s actually a complex region, delimited by muscles and fascia, and it contains a lot of vessels and nerves that pass from the thigh to the leg.

So first, let’s look at the popliteal fossa, which, superficially, resembles a diamond-shaped cavity when the knee is slightly flexed. This means the popliteal fossa has two superior borders and two inferior borders.

So, lets go over these borders; The two superior ones are the superolateral border, delimited by the biceps femoris; and the superomedial border, delimited by the semimembranosus and semitendinosus muscles.

The two inferior borders are the inferomedial border, represented by the medial head of the gastrocnemius muscle, and the inferolateral border, delimited by the lateral head of the gastrocnemius muscle. The popliteal fossa also has a floor and a roof. The roof consists of two layers: the popliteal fascia and skin.

However, things get a bit more complicated with the floor, which has three sections: the bony popliteal surface of the femur superiorly, the posterior aspect of the joint capsule of the knee joint centrally, and the popliteus muscle and fascia covering the popliteus muscle inferiorly.

The popliteal fossa contains the small saphenous vein; the posterior cutaneous nerve of the thigh; the sciatic nerve, which divides into the tibial and common fibular nerves at the superior border; the popliteal arteries and veins along with their branches and tributaries; and the popliteal lymph nodes and lymphatic vessels.

Ok, so now let’s dive in with a little bit more detail, layer by layer. First, there’s the subcutaneous or superficial fascia, which contains the small saphenous vein, the terminal branch of the posterior cutaneous nerve of the thigh, and the medial and lateral sural cutaneous nerves.