The area behind the knee, though less visible, plays a significant role in lower limb function. Understanding this posterior region is important for comprehending the knee’s overall mechanics and potential issues. This article clarifies the anatomical name for the back of the knee, details the structures found there, and discusses common conditions that may affect this region.
The Proper Anatomical Term
The area behind the knee is anatomically known as the Popliteal Fossa. This depression forms a diamond-shaped space located on the posterior aspect of the knee joint. The Popliteal Fossa acts as a passageway for various important vessels and nerves traveling between the thigh and lower leg.
The boundaries of this diamond-shaped region are formed by specific muscle groups. Above and towards the inner side, the semitendinosus and semimembranosus muscles define its border. On the outer upper side, the biceps femoris muscle forms the boundary. Below, the medial and lateral heads of the gastrocnemius (calf muscle) contribute to the lower borders of the Popliteal Fossa.
Key Structures of the Area
The Popliteal Fossa contains several important anatomical structures integral to lower limb function. Deep within this space lies the popliteal artery, a continuation of the femoral artery from the thigh. This artery supplies oxygenated blood to the knee, lower leg, and foot. Running alongside is the popliteal vein, which collects deoxygenated blood from the lower leg and foot, returning it towards the heart.
Two major nerves, branches of the sciatic nerve, also traverse this region: the tibial nerve and the common fibular nerve. The tibial nerve provides motor control to muscles in the back of the leg and foot, enabling movements like pointing the toes, and carries sensory information from the sole of the foot. The common fibular nerve wraps around the side of the knee and supplies muscles that lift the foot and toes, providing sensation to the front and outer part of the lower leg and top of the foot.
Additionally, the Popliteal Fossa houses popliteal lymph nodes, small clusters of immune cells. These nodes filter lymphatic fluid from the lower leg and foot, trapping pathogens like bacteria and viruses. They contribute to the body’s immune defense system, maintaining overall leg health.
Common Conditions Affecting the Back of the Knee
A common condition affecting the Popliteal Fossa is a Baker’s cyst, also known as a popliteal cyst. This fluid-filled lump forms behind the knee, often due to excess fluid within the knee joint, associated with conditions like arthritis or meniscus tears. Symptoms include fullness, pain, or stiffness at the back of the knee, and sometimes lower leg swelling.
Another condition is Popliteal Artery Entrapment Syndrome (PAES), where calf muscles compress the popliteal artery. This compression can restrict blood flow to the lower leg, leading to pain or cramping in the calf during exercise that typically resolves with rest. This condition primarily affects young, active individuals.
Nerve compression can also occur in this area, particularly affecting the tibial or common fibular nerves. Compression can result in symptoms such as pain, tingling, numbness, or weakness in the lower leg or foot, depending on the affected nerve. These sensations arise when pressure disrupts nerve function.