The iliacus is a flat, triangular muscle which fills the

iliac fossa The iliac fossa is a large, smooth, concave surface on the internal surface of the Ilium (bone), ilium (part of the three fused bones making the hip bone). Structure The iliac fossa is bounded above by the iliac crest, and below by the Arcuate ...

. It forms the

lateral Lateral is a geometric term of location which may also refer to: Biology and healthcare * Lateral (anatomy), a term of location meaning "towards the side" * Lateral cricoarytenoid muscle, an intrinsic muscle of the larynx * Lateral release ( ...

portion of iliopsoas, providing

flexion Motion, the process of movement, is described using specific anatomical terminology, anatomical terms. Motion includes movement of Organ (anatomy), organs, joints, Limb (anatomy), limbs, and specific sections of the body. The terminology used de ...

of the thigh and

lower limb Lower may refer to: *Lower (album), ''Lower'' (album), 2025 album by Benjamin Booker *Lower (surname) *Lower Township, New Jersey *Lower Receiver (firearms) *Lower Wick Gloucestershire, England See also

*Nizhny {{Disambiguation ...

at the acetabulofemoral joint.

Structure

The iliacus arises from the

on the interior side of the

hip bone The hip bone (os coxae, innominate bone, pelvic bone or coxal bone) is a large flat bone, constricted in the center and expanded above and below. In some vertebrates (including humans before puberty) it is composed of three parts: the Ilium (bone) ...

, and also from the region of the anterior inferior iliac spine (AIIS). It joins the psoas major to form the iliopsoas. It proceeds across the iliopubic eminence through the muscular lacuna to its insertion on the lesser trochanter of the

femur The femur (; : femurs or femora ), or thigh bone is the only long bone, bone in the thigh — the region of the lower limb between the hip and the knee. In many quadrupeds, four-legged animals the femur is the upper bone of the hindleg. The Femo ...

. Its fibers are often inserted in front of those of the psoas major and extend distally over the lesser trochanter.Platzer (2004), p 234

Nerve supply

The iliopsoas is innervated by the femoral nerve and direct branches from the lumbar plexus.''Thieme Atlas of Anatomy'' (2006), p 422

Function

In open-chain exercises, as part of the iliopsoas, the iliacus is important for lifting (flexing) the femur forward (e.g. front scale). In closed-chain exercises, the iliopsoas bends the trunk forward and can lift the trunk from a lying posture (e.g. 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 In vertebrate anatomy, the hip, or coxaLatin ''coxa'' was used by Celsus in the sense "hip", but by Pliny the Elder in the sense "hip bone" (Diab, p 77) (: ''coxae'') in medical terminology, refers to either an anatomical region or a joint o ...

Additional images

File:Iliacus muscle - animation05.gif, Position of iliacus muscle (shown in red). Animation. File:Gray236.png, Right

. Internal surface. Iliac fossa visible at upper left.

Notes

References

* *

External links

PTCentral
* - "Muscles and nerves of the posterior abdominal wall." * (, ) {{Authority control Hip flexors Hip muscles Iliopsoas muscles Muscles of the lower limb