Iliococcygeus
Pelvis & Perineum · Trunk
The iliococcygeus is one of the sheet-like components of the levator ani, the muscular hammock that forms the greater part of the pelvic floor. Rather than arising from bone directly, it takes origin from the ischial spine and the posterior part of the tendinous arch of the obturator fascia, a thickened line running along the side wall of the pelvis. Its fibres sweep downward and medially to meet those of the opposite side at the anococcygeal ligament, or raphe, and the coccyx. In this way the two iliococcygeus muscles form a supporting shelf beneath the pelvic viscera. Its role is to support and elevate the pelvic floor and the organs resting on it, resisting the downward pressure generated during coughing, straining, and lifting. It is supplied by the nerve to levator ani, arising from the anterior ramus of S4, with a contribution from the pudendal nerve (S2-S4).
Origin, Insertion, Action & Nerve
Origin
Ischial spine and posterior part of the tendinous arch of the obturator fascia
Insertion
Anococcygeal ligament (raphe) and coccyx
Action
Supports and elevates the pelvic floor and viscera
Nerve
Nerve to levator ani (anterior ramus of S4) and the pudendal nerve (S2–S4)
Attachments explained
The Iliococcygeus 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
Ischial spine and posterior part of the tendinous arch of the obturator fascia
Insertion
Anococcygeal ligament (raphe) and coccyx
Action & function
When the Iliococcygeus contracts, it produces the following movement: Supports and elevates the pelvic floor and viscera.
As part of the Pelvis & Perineum group of the Trunk, it works alongside neighbouring muscles to generate smooth, coordinated movement and to stabilise the structures it acts on.
Nerve supply & clinical relevance
The Iliococcygeus receives its nerve supply from the Nerve to levator ani (anterior ramus of S4) and the pudendal nerve (S2–S4). This nerve carries fibres from spinal segment(s) S4, S2.
Because a muscle can only contract when its nerve is intact, injury to the Nerve to levator ani or to its spinal roots (S4, S2) can weaken or paralyse the Iliococcygeus, impairing the movements it normally produces (supports and elevates the pelvic floor and viscera). This is why knowing the innervation is central to localising nerve lesions in clinical practice.
How to study the Iliococcygeus (the OIANS method)
Fix the iliococcygeus in your mind as the posterolateral part of the levator ani that spans the gap between the pelvic side wall and the midline. Because it starts on the ischial spine and the tendinous arch and ends on the anococcygeal raphe and coccyx, picture it as a curtain slung from wall to wall; that image alone explains its supporting and elevating action on the pelvic floor. Contrast it with the more anterior pubococcygeus, which starts on the pubis instead of the ischial spine.
Anchor the nerve supply by remembering that the levator ani is approached from two sides: its pelvic surface receives the nerve to levator ani (S4) and its perineal aspect receives twigs from the pudendal nerve (S2-S4). Reciting that dual supply for iliococcygeus lets you carry it across to pubococcygeus and puborectalis, which share the same innervation, so one fact covers the whole levator ani group.
Frequently asked questions
Where is the Iliococcygeus located?
The Iliococcygeus is a muscle of the Pelvis & Perineum group, located in the Trunk.
What is the origin of the Iliococcygeus?
Ischial spine and posterior part of the tendinous arch of the obturator fascia
What is the insertion of the Iliococcygeus?
Anococcygeal ligament (raphe) and coccyx
What movements does the Iliococcygeus produce?
Supports and elevates the pelvic floor and viscera
What nerve supplies the Iliococcygeus?
Nerve to levator ani (anterior ramus of S4) and the pudendal nerve (S2–S4)
Is the Iliococcygeus free to study in OIANS?
The Iliococcygeus 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 Trunk 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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