Iliopsoas

The ileopsoas muscle is often considered as a single biarticular muscle, located in the low back region and in the anterior region of the thigh. In reality it is formed by two distinct portions: the large psoas muscle, and the iliac muscle.

It originates from the lateral faces of the bodies of the last thoracic vertebra, from the first four lumbar vertebrae and from the interposed disks, and from the base of the transverse processes of the first four lumbar vertebrae. The muscular body moves obliquely down and out; passes under the inguinal ligament and, having reached the thigh, ends at the apex of the small trochanter. The femoral nerve runs between the iliac muscle and the large psoas.

With its action it flexes and rotates the thigh externally; flexes and tilts the trunk laterally. Being the most powerful thigh flexor it has a very important role in walking.

Participates in maintaining the physiological balance of the pelvis, increasing lumbar lordosis with its contraction. (lordosizing effect. It therefore favors the anteversion of the pelvis, and its hypertonus can cause annoying lumbago (See: Importance of the abdominal muscles in the prevention of low back pain)

It is innervated by the femoral nerve and the branches of the lumbar plexus (L1-L4).

ORIGIN

Intervertebral bodies and discs of T12-L4, costal processes of L1-L4 and inner lip of the iliac crest; anterior iliac flank, 2/3 superior of the iliac fossa, ileolombar ligament, wing of the sacrum