Iliacus m.

The iliacus is a flat, triangular muscle which fills the iliac fossa.

The iliacus arises from the iliac fossa on the interior side of the hip bone, and also from the region of the anterior inferior iliac spine (AIIS). It joins the psoas major to form the Iliopsoas as which it proceeds across the iliopubic eminence through the muscular lacuna to its insertion on the lesser trochanter of the femur. Its fibers are often inserted in front of those of the psoas major and extends distally over the lesser trochanter.

The iliopsoas is innervated by the femoral nerve and direct branches from the lumbar plexus.