Coccygeus

Origin, Insertion, Action & Nerve

Attachments explained

The Coccygeus 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.

Action & function

When the Coccygeus contracts, it produces the following movement: Supports the pelvic viscera and pulls the coccyx forward after defecation.

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 Coccygeus receives its nerve supply from the Anterior rami of S4–S5. This nerve carries fibres from spinal segment(s) S4, S5.

Because a muscle can only contract when its nerve is intact, injury to the Anterior rami of S4–S5 or to its spinal roots (S4, S5) can weaken or paralyse the Coccygeus, impairing the movements it normally produces (supports the pelvic viscera and pulls the coccyx forward after defecation). This is why knowing the innervation is central to localising nerve lesions in clinical practice.

How to study the Coccygeus (the OIANS method)

OIANS stands for Origin, Insertion, Action and Nerve, the four facts that uniquely define every skeletal muscle. To learn the Coccygeus, 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 Coccygeus 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.

Coccygeus quick facts

Region

Trunk

Group

Pelvis & Perineum

Origin

Ischial spine and sacrospinous ligament

Insertion

Lateral margin of the coccyx and lowest part of the sacrum

Action

Supports the pelvic viscera and pulls the coccyx forward after defecation

Nerve

Anterior rami of S4–S5

Spinal roots

S4, S5

Frequently asked questions

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