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Iliopsoas muscle

Origins, insertions, innervation and functions of the iliopsoas muscle.

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Hello again, everyone! It’s Matt from Kenhub, and in this tutorial, we will discuss the anatomy, innervation, and function of the iliopsoas muscle.

The iliopsoas muscle belongs to the inner hip muscles. It consists of a complex of two muscles with different areas of origin.

The iliopsoas belongs to the striated musculature, and the innervation is carried by the femoral nerve as well as the direct branches of the lumbar plexus, both seen highlighted in green on these images.

The iliopsoas muscle consists of the psoas major and the iliacus muscles.

The psoas major muscle originates from the first to fourth lumbar vertebrae, the costal processes of all lumbar vertebrae, and the twelfth thoracic vertebrae and inserts at the lesser trochanter of the femur.

The iliacus muscle originates from the iliac fossa and inserts with the psoas major at the lesser trochanter. The psoas major and the 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.

The iliopsoas muscle is the strongest flexor of the hip joint, which makes it an important muscle for walking. In the supine position, it decisively supports the straightening of the upper body. For example, 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.

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