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 The iliopsoas muscle (; ) refers to the joined psoas major and the iliacus muscles. The two muscles are separate in the abdomen, but usually merge in the thigh. They are usually given the common name ''iliopsoas''. The iliopsoas muscle joins t ...

, 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 In anatomy, the thigh is the area between the hip (pelvis) and the knee. Anatomically, it is part of the lower limb. The single bone in the thigh is called the femur. This bone is very thick and strong (due to the high proportion of bone tissu ...

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 The anterior inferior iliac spine (AIIS) is a bony eminence on the anterior border of the hip bone, or, more precisely, the wing of the ilium. Structure The AIIS is a bony eminence on the anterior border of the ilium. It is below the anterior ...

(AIIS). It joins the

psoas major The psoas major ( or ; from ) is a long fusiform muscle located in the lateral lumbar region between the vertebral column and the brim of the lesser pelvis. It joins the iliacus muscle to form the iliopsoas. In other animals, this muscle is e ...

to form the

. It proceeds across the

iliopubic eminence Medial to the anterior inferior iliac spine is a broad, shallow groove, over which the iliacus and psoas major muscles pass. This groove is bounded medially by an eminence, the iliopubic eminence (or iliopectineal eminence), which marks the poin ...

through the

muscular lacuna The muscular lacuna (Latin: ''lacuna musculorum'') is the lateral compartment of the thigh beneath the inguinal ligament. It is separated from the medial vascular lacuna by the iliopectineal arch. It is occupied/traversed by the iliopsoas muscle, ...

to its insertion on the

lesser trochanter In human anatomy, the lesser trochanter is a conical, posteromedial, bony projection from the shaft of the femur. It serves as the principal insertion site of the iliopsoas muscle. Structure The lesser trochanter is a conical posteromedial p ...

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

.Platzer (2004), p 234

Nerve supply

The iliopsoas is innervated by the

femoral nerve The femoral nerve is a nerve in the thigh that supplies skin on the upper thigh and inner leg, and the muscles that extend the knee. It is the largest branch of the lumbar plexus. Structure The femoral nerve is the major nerve supplying the ant ...

and direct branches from the

lumbar plexus The lumbar plexus is a web of nerves (a nerve plexus) in the lumbar region of the body which forms part of the larger lumbosacral plexus. It is formed by the divisions of the first four lumbar nerves (L1–L4) and from contributions of the su ...

.''Thieme Atlas of Anatomy'' (2006), p 422

Function

open-chain exercises Open chain exercises (OKE) are exercises that are performed where the hand or foot is free to move. The opposite of OKE are closed kinetic chain exercises (CKE). Both are effective for strengthening and rehabilitation objectives. Closed-chain exerc ...

, as part of the

, the iliacus is important for lifting (flexing) the femur forward (e.g.

front scale Front may refer to: Arts, entertainment, and media Films * ''The Front'' (1943 film), a 1943 Soviet drama film * '' The Front'', 1976 film Music * The Front (band), an American rock band signed to Columbia Records and active in the 1980s and ...

). In

closed-chain exercises Closed kinetic chain exercises or closed chain exercises (CKC) are physical exercises performed where the hand (for arm movement) or foot (for leg movement) is fixed in space and cannot move. The extremity remains in constant contact with the immob ...

, the iliopsoas bends the trunk forward and can lift the trunk from a lying posture (e.g.

sit-ups The sit-up is an abdominal endurance training exercise to strengthen, tighten and tone the abdominal muscles. It is similar to a curl-up (that targets the rectus abdominis and also works the external and internal obliques), but sit-ups have a ...

back scale The human back, also called the dorsum (: dorsa), is the large posterior area of the human body, rising from the top of the buttocks to the back of the neck. It is the surface of the body opposite from the chest and the abdomen. The vertebral c ...

) because the psoas major crosses several vertebral joints and the

sacroiliac joint The sacroiliac joint or SI joint (SIJ) is the joint between the sacrum and the ilium bones of the pelvis, which are connected by strong ligaments. In humans, the sacrum supports the spine and is supported in turn by an ilium on each side. The ...

. 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