In the posterior thigh, a crucial network of blood vessels forms an intersection known as the cruciate anastomosis. This cross-shaped connection acts as a natural bypass, creating an alternative route for blood flow between the internal iliac and popliteal arteries. Its primary function is to provide collateral circulation, ensuring the lower limb remains supplied with blood even if the femoral artery is obstructed.

This network is formed by four key vessels converging around the proximal femur, specifically near the quadratus femoris muscle and at the level of the lesser trochanter.

The structure of the cruciate anastomosis depends on the precise paths of four distinct arterial branches.

2. Medial Circumflex Femoral Artery: The transverse branch of this artery travels posteriorly, passing between the quadratus femoris and the upper border of the adductor magnus muscle to join the network. It supplies blood from a medial-to-lateral direction.

3. Lateral Circumflex Femoral Artery: Its transverse branch crosses the vastus lateralis muscle, pierces it, and wraps around the femur to contribute to the anastomosis from the lateral side.

These four vessels don't just meet randomly; they converge in a specific anatomical location. The intersection occurs on the posterior aspect of the femur, at the level of the lesser trochanter. The quadratus femoris muscle serves as a key landmark, with the anastomosis forming just inferior to it.

This anatomical arrangement provides a robust link between the arterial supply of the pelvis (via the internal iliac artery, which gives rise to the inferior gluteal artery) and the deep artery of the thigh (profunda femoris). In cases of femoral artery blockage proximal to the origin of the profunda femoris, this anastomosis allows blood to bypass the obstruction and continue down to the popliteal artery, preserving circulation to the leg.