Iliacus
Gluteal & Hip · Lower Limb
The Iliacus is found among the Gluteal & Hip muscles of the Lower Limb. It arises from Iliac fossa, ala of sacrum, and anterior sacroiliac ligaments and attaches to Lesser trochanter of femur (with psoas major tendon as iliopsoas). It is responsible for several movements: Flexion of hip; assists flexion of trunk. Innervation is provided by the Femoral nerve (L2, L3).
Origin, Insertion, Action & Nerve
Origin
Iliac fossa, ala of sacrum, and anterior sacroiliac ligaments
Insertion
Lesser trochanter of femur (with psoas major tendon as iliopsoas)
Action
Flexion of hip; assists flexion of trunk
Nerve
Femoral nerve (L2, L3)
Attachments explained
The Iliacus is defined first by where it attaches. Its origin is the more fixed anchor, usually the proximal or more stable end that stays put during contraction, while its insertion is the more mobile point that is pulled toward the origin when the muscle shortens.
Origin
Iliac fossa, ala of sacrum, and anterior sacroiliac ligaments
Insertion
Lesser trochanter of femur (with psoas major tendon as iliopsoas)
Action & function
When the Iliacus contracts, it produces the following movements: Flexion of hip; assists flexion of trunk.
As part of the Gluteal & Hip group of the Lower Limb, it works alongside neighbouring muscles to generate smooth, coordinated movement and to stabilise the structures it acts on.
Nerve supply & clinical relevance
The Iliacus receives its nerve supply from the Femoral nerve (L2, L3). This nerve carries fibres from spinal segment(s) L2, L3.
Because a muscle can only contract when its nerve is intact, injury to the Femoral nerve or to its spinal roots (L2, L3) can weaken or paralyse the Iliacus, impairing the movements it normally produces (flexion of hip). This is why knowing the innervation is central to localising nerve lesions in clinical practice.
How to study the Iliacus (the OIANS method)
OIANS stands for Origin, Insertion, Action and Nerve, the four facts that uniquely define every skeletal muscle. To learn the Iliacus, work through them in order: picture its origin, trace the muscle to its insertion, reason out the action that shortening between those two points must create, then add the nerve that drives it.
Most students remember the Iliacus fastest by linking its action back to its attachments rather than memorising each fact in isolation. Once the origin and insertion make sense, the action usually follows logically.
Iliacus quick facts
- Region
- Lower Limb
- Group
- Gluteal & Hip
- Origin
- Iliac fossa, ala of sacrum, and anterior sacroiliac ligaments
- Insertion
- Lesser trochanter of femur (with psoas major tendon as iliopsoas)
- Action
- Flexion of hip; assists flexion of trunk
- Nerve
- Femoral nerve (L2, L3)
- Spinal roots
- L2, L3
Frequently asked questions
Where is the Iliacus located?
The Iliacus is a muscle of the Gluteal & Hip group, located in the Lower Limb.
What is the origin of the Iliacus?
Iliac fossa, ala of sacrum, and anterior sacroiliac ligaments
What is the insertion of the Iliacus?
Lesser trochanter of femur (with psoas major tendon as iliopsoas)
What movements does the Iliacus produce?
Flexion of hip; assists flexion of trunk
What nerve supplies the Iliacus?
Femoral nerve (L2, L3)
Is the Iliacus free to study in OIANS?
The Iliacus is always free to browse. Its full origin, insertion, action and nerve details are open to everyone in the Muscle Directory. Quiz and Flashcard practice for the Lower Limb is part of the one-time Lifetime upgrade, though; only the Upper Limb decks are free to test yourself on.
Related muscles
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