The indentation behind the knee, commonly called the “hollow of the thigh,” is a recognizable anatomical landmark. While its location is familiar, its precise structure and the important elements it contains are not widely known. This region serves as a crucial pathway for various bodily components, connecting the thigh to the lower leg. Understanding this area provides insight into its significance.
Precise Anatomical Definition
The “hollow of the thigh” is medically known as the popliteal fossa, a diamond-shaped depression at the back of the knee joint. This space is formed by muscles that create its distinct boundaries. The upper and inner border is defined by the semimembranosus and semitendinosus muscles, while the upper and outer border is formed by the biceps femoris muscle.
Below the knee, the two heads of the gastrocnemius muscle establish the lower medial and lateral boundaries of the fossa. The floor of this diamond-shaped space is composed of the posterior surface of the femur (thigh bone), the capsule of the knee joint, and the popliteus muscle. Overlying these structures, the roof of the popliteal fossa is formed by skin and layers of fascia.
Vital Components Within
The popliteal fossa houses several important structures that facilitate function in the lower limb. These include the popliteal artery and popliteal vein. The popliteal artery, a continuation of the femoral artery, carries oxygen-rich blood from the thigh to the lower leg and foot, supplying muscles around the knee and calf. The popliteal vein, positioned just behind the artery, returns deoxygenated blood from the lower leg back towards the heart.
Two major branches of the sciatic nerve, the tibial nerve and the common fibular nerve, also traverse this region. These nerves are responsible for providing sensation to parts of the lower leg and foot, as well as controlling muscle movement in these areas. The tibial nerve supplies muscles that allow for plantarflexion (pointing the foot down) and inversion (turning the sole inward), while the common fibular nerve controls dorsiflexion (lifting the foot) and eversion (turning the sole outward).
Practical Importance
Understanding the popliteal fossa is important for medical assessment and injury management. The popliteal artery serves as a pulse point, and healthcare providers often check the popliteal pulse to assess blood flow to the lower leg, especially in cases of peripheral artery disease or injury. While sometimes difficult to locate, its presence indicates adequate circulation.
This region is a common site for medical procedures, such as nerve blocks for pain management or surgery involving the foot and ankle. Anesthesia administered in the popliteal fossa can effectively block sensation and movement below the knee, while often preserving the function of hamstring muscles. Damage to the popliteal fossa, particularly from blunt trauma or knee dislocations, can have serious consequences. Injuries to the popliteal artery can lead to reduced blood flow, potentially resulting in tissue damage or, in severe cases, requiring amputation if not treated promptly.