Iliac

The iliac muscle is a broad and powerful muscle located on the internal surface of the ilium. Together with the psoas major, it forms the iliopsoas muscle, the main flexor of the hip joint. Its structure is generally thick and fleshy, with fine fascicles converging toward its ventrocaudal part, where they become slightly tendinous. A deep groove, intended to accommodate the psoas major, partially divides it into two portions, the lateral one being the largest and thickest.

Origin: The muscle arises from the pelvic surface of the ilium. Its origin extends widely to the border of the iliac crest and the nearby region of the arcuate line, reaching the angle of the hip. It may also anchor to the ventral sacroiliac ligament and, depending on the species, to a small area of the sacrum or to the body of the last lumbar vertebra.

Insertion: The muscle ends in a common tendon with the psoas major. Together, they form the iliopsoas muscle, whose tendon attaches to the lesser trochanter of the femur.

Relations: The ventral surface of the iliacus muscle is partially covered by the psoas major and lined by the fascia iliaca. Caudally, it is successively overlain by the inguinal arch, the transverse and internal oblique abdominal muscles, and finally by the sartorius muscle. Its dorsal surface lies directly against the ilium and the sacroiliac joint, while near its insertion, it is related to the hip joint. Its lateral border is separated from the tensor fasciae latae and the origin of the rectus femoris by a broad space filled with connective and adipose tissue.

Action: The iliacus muscle acts together with the psoas major to flex the hip, bringing the thigh toward the abdomen. They also participate in external rotation and adduction of the femur, as well as in the stabilization of the hip joint and the vertebral column.

Innervation: The innervation comes from the ventral branches of the last lumbar nerves, particularly from the femoral nerve, which provides the main motor supply.

Vascularization: The vascular supply arises from branches of the lumbar arteries and veins, the deep circumflex iliac arteries and veins, as well as from branches of the internal iliac artery accompanied by their satellite veins.