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Iliacus muscle

Recommended video: Inner hip muscles [09:58]
Origins, insertions, innervation and functions of the inner hip muscles.
Iliacus muscle (Musculus iliacus)

Iliacus is a triangular muscle of the iliac region which together with the psoas major, comprises the iliopsoas muscle. The iliacus muscle belongs the group of the inner hip muscles, together with the psoas major, psoas minor, obturator externus, obturator internus, superior gemellus, inferior gemellus, piriformis, and quadratus femoris muscles.

As a group, the inner hip muscles act upon the hip joint. The function of the iliacus muscle in particular is described together with that of the psoas major, i.e. from the aspect of the iliopsoas muscle. Having said that, the iliopsoas is the chief flexor of the hip joint. It also contributes to the lateral flexion of the trunk. However, the latter movement is produced by the psoas major muscle only, without any involvement of the iliacus muscle.

This article will discuss the anatomy and function of the iliacus muscle.

Key facts about the iliacus muscle
Origin Iliac fossa
Insertion Lesser trochanter of femur
Action Hip joint: Thigh/trunk flexion
Innervation Femoral nerve (L1-L3)
Blood supply Iliolumbar, deep circumflex iliac, obturator, and femoral arterie
  1. Origin and insertion
  2. Relations
  3. Innervation
  4. Blood supply
  5. Function
  6. Clinical relations
    1. Shortening of the iliacus muscle
  7. Sources
+ Show all

Origin and insertion

The iliacus muscle has a vast origin, the majority of it arising from the superior two-thirds of the iliac fossa. The rest arises from several other origin points, which are the inner lip of the iliac crest, the lateral aspect of the sacrum and anterior sacroiliac and iliolumbar ligaments. The muscle fibers converge distally towards the hip, thus contributing to the triangular shape of this muscle.

At the level of the capsule of the hip joint, the iliacus muscle fibers blend with those of the psoas major muscle, forming a common tendon for the iliopsoas. The tendon of iliopsoas crosses the anterior surface of the hip joint to finally insert to the lesser trochanter of femur. Before insertion, the tendon of iliopsoas receives a small slip called the iliocapsularis muscle, which is a small muscle lying just superficial to the hip joint capsule.

All these origins and insertions can get quite overwhelming when there’s more than 600 muscles in the body! Learn them faster with our condense muscle anatomy reference charts!


The anterior surface of the pelvic part of the iliacus muscle is covered with the iliac fascia, which separates it from the peritoneum. This surface of the iliacus is also crossed by the lateral femoral cutaneous nerve, the cecum on the right side, and the iliac part of the descending colon on the left side. The medial margin of the iliacus muscle is in relation with the femoral nerve and lateral margin of the psoas major muscle.

The anterior surface of the thigh portion of the iliacus muscle lies posterior to the fascia lata, rectus femoris and sartorius muscles. It is also crossed by the deep femoral artery (profunda femoris). The posterior surface of the iliacus is adjacent to the hip joint, from which it is separated by a large subtendinous iliac bursa.

Master the anatomy of the hip and thigh muscles with our videos, quizzes, labelled diagrams, and articles:


The iliacus muscle is innervated by the femoral nerve (L2-L4).

Blood supply

Just like the psoas major muscle, the iliacus is mainly supplied by the iliolumbar artery. Additionally, it receives the blood from the deep circumflex iliac, obturator, and femoral arteries.


The iliacus muscle works in synergy with the psoas major muscle to produce movements in the hip joint. When its proximal attachment is fixed, the muscle contributes to the flexion of the thigh. On the other hand, with its distal attachment fixed, the muscle helps to bring the trunk forwards against resistance. These actions are essential for lower limb functions such as walking, running and jumping.

Whenever you’re ready to round up the story about the hip and thigh muscles, try out our quiz below:

Iliacus muscle: want to learn more about it?

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