The popliteal fossa is a diamond shaped area found on the posterior side of the knee. It is the main path in which structures move from the thigh to the leg.
In any anatomical area such as this, it is important to look at the borders, contents, and any clinical relevance.
Borders of the Popliteal Fossa
The borders are formed by the muscles in the posterior compartment of the leg and thigh.
- Superior and medial border: Semimembranosus.
- Superior and lateral border: Biceps femoris.
- Inferior and medial border: Medial head of the gastrocnemius.
- Inferior and lateral border: Lateral head of the gastrocnemius and plantaris.
The popliteal fossa also has a floor and a roof. The floor of the popliteal fossa is formed by the posterior surface of the knee joint capsule, and by the posterior surface of the femur. The roof is made of up two layers; popliteal fascia and skin. The popliteal fascia is continuous with the fascia lata of the leg.
Contents of the Popliteal Fossa
The main contents of the popliteal fossa are:
- Popliteal artery
- Popliteal vein
- Small saphenous vein
- Tibial nerve
- Common fibular nerve
The tibial and common fibular nerves are the most superficial of the contents of the popliteal fossa. They are both branches of the sciatic nerve. The common fibular nerve follows the biceps femoris tendon, running along the lateral margin of the popliteal fossa.
The small saphenous vein pierces the popliteal fascia of the popliteal fossa to enter the diamond, and empty into the popliteal vein.
In the popliteal fossa, the deepest structure in the popliteal artery. It is a continuation of the femoral artery, and travels into the leg to supply it with blood.
Clinical Relevance: Popliteal Aneurysm
An aneurysm is a dilation of an artery, which is greater than 50% of the normal diameter. The popliteal fascial layer (the roof of the popliteal fossa) is tough and non extensible, and so an aneurysm of the popliteal artery has consequences for the other contents of the popliteal fossa.
The tibial nerve is particularly susceptible to compression from the popliteal artery. Damage to this nerve will present as leg anesthesia, or loss of leg motor function.
An aneurysm of the popliteal artery can be detected by an obvious palpable pulsation in the popliteal fossa, with abnormal arterial sounds.