Iliacus

Iliacus muscle
Position of iliacus muscle (shown in red.)
The iliacus and nearby muscles
Details
Origin	upper two-third of the iliac fossa
Insertion	base of the lesser trochanter of femur
Artery	medial femoral circumflex artery, iliac branch of iliolumbar artery
Nerve	femoral nerve
Actions	flexes and rotates laterally thigh
Antagonist	Gluteus maximus
Identifiers
Latin	musculus iliacus
TA	A04.7.02.003
FMA	22310
Anatomical terms of muscle []

The iliacus (/ᵻˈlaɪ.əkəs/) 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.

In open-chain exercises, as part of the iliopsoas, the iliacus is important for lifting (flexing) the femur forward (i.e. front scale). In closed-chain exercises, the iliopsoas bends the trunk forward and can lift the trunk from a lying posture (i.e. sit-ups, back scale) because the psoas major crosses several vertebral joints and the sacroiliac joint. From its origin in the lesser pelvis the iliacus acts exclusively on the hip joint.