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Iliopsoas Muscle

The iliopsoas muscle belongs to the inner hip muscles. It is actually built out of the two muscles, psoas major and iliacus muscles, which are separated in the abdomen, but later merge and share the same insertion in the thigh.

This is the deeply located muscle that is essential for the posture of the human body. Interesting is that the more the muscle is trained, the child birth is going to be faster and easier. So if someone within the female gender is interested in that, abs workout is recommended, since this muscle is a flexor.

Key Facts
Origin Psoas major: the bodies of the vertebrae T12-L4 and costal processes of the vertebrae L1-L5
Iliacus: iliac fossa
Insertion Lesser trochanter of the femur
Vascularization Medial femoral circumflex artery, iliolumbar artery
Innervation Femoral nerve, branches of the lumbar plexus (L1-L3)
Actions Flexion of hip
Antagonist muscle Gluteus maximus muscle and the posterior compartment of the thigh

All of the important anatomical facts about the iliopsoas muscle will be described in this article.


It comprises a complex of two muscles with different areas of origin. This muscle belongs to the striated musculature and the innervation is carried by the femoral nerve as well as direct branches of the lumbar plexus.

The iliopsoas muscle consists of:

  • Psoas major muscle - originates from the bodies of the vertebrae T12-L4 and the costal processes of the vertebrae L1-L5. (The muscle inserts at the lesser trochanter of the femur, as the iliopsoas muscle).
  • Iliacus muscle - runs from the iliac fossa to the lesser trochanter.

Relations & Location

The psoas major and iliacus muscle unify in the lateral pelvis shortly before the inguinal ligament, becoming the iliopsoas muscle. There they pass below the inguinal ligament through the muscular lacuna together with the femoral nerve. Both muscles are completely surrounded by the iliac fascia. The lumbar plexus lies dorsally from the psoas major muscle which is penetrated by the genitofemoral nerve. Medially from the psoas major runs the sympathetic trunk.

Recommended video: Iliopsoas muscle
Origins, insertions, innervation and functions of the iliopsoas muscle.


The iliopsoas muscle is the strongest flexor of the hip joint (important walking muscle). In the supine position it decisively supports the straightening of the upper body (e.g. during sit-ups). Furthermore it rotates the thigh laterally. A unilateral contraction leads to a lateral flexion of the lumbar vertebrae column. Altogether the iliopsoas muscle plays a significant role in the movement and stabilization of the pelvis.

Clinical Aspects

Abrupt movements (e.g. shooting the soccer ball) and overload may cause an inflammation of the tendon or the associated bursa (iliopsoas syndrome). A pathological shortening of the muscle leads to hyperlordosis of the lumbar vertebrae column over the long term due to unnatural and incorrect strain.

In rare cases an abscess (e.g. in bacterial spondylodiscitis) can spread within the iliac fascia and the muscle compartment until it reaches the lesser trochanter (psoas abscess).

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Show references


  • D. Drenckhahn/J. Waschke: Taschenbuch Anatomie, 1.Auflage, Urban & Fischer Verlag/Elsevier (2008), S.76-77
  • M. Schünke/E. Schulte/U. Schumacher: Prometheus – LernAtlas der Anatomie – Allgemeine Anatomie und Bewegungssystem, 2.Auflage, Thieme Verlag (2007), S.152-153, 202
  • J. Weineck: Sportanatomie, 16.Auflage, Spitta Verlag (2003), S.152-154
  • A. Stäbler/B. Erlt-Wanger: Radiologie-Trainer, 11.Auflage, Thieme Verlag (2006), S.145

Author & Layout:

  • Achudhan Karunaharamoorthy
  • Christopher A. Becker


  • First Illustration Gallery - Liene Znotina
  • Second Illustration Gallery - Liene Znotina
  • Third Illustration Gallery - Paul Kim
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