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[Joints and ligaments](https://durgical.com/en/anatomy/system/joints-and-ligaments/) · [Lower limb](https://durgical.com/en/anatomy/region/lower-limb/)

# Sacrospinous ligament

The sacrospinous ligament is a short band from the [sacrum](https://durgical.com/en/anatomy/sacrum/) to a bony spine on the [hip bone](https://durgical.com/en/anatomy/hip-bone/); it steadies the [pelvis](https://durgical.com/en/anatomy/region/pelvis/).

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## What it is

A short, triangular band from the sacrum and [coccyx](https://durgical.com/en/anatomy/coccyx/) to the ischial spine, a point on the hip bone.

## What it does

Steadies the sacrum and helps form the openings through which the sciatic nerve and other nerves leave the pelvis.

## Key points

- The [pudendal nerve](https://durgical.com/en/anatomy/pudendal-nerve/), internal pudendal vessels and nerve to [obturator internus](https://durgical.com/en/anatomy/obturator-internus/) cross behind it at the ischial [spine](https://durgical.com/en/anatomy/region/spine/), leaving the greater sciatic foramen and entering the lesser
- Landmark for the transvaginal pudendal nerve block, aimed just behind the ischial spine
- Coccygeus lies on its pelvic surface; the ligament is regarded as the fibrous back part of that muscle

## Key facts

**Attaches**
Lateral sacrum and coccyx to ischial spine

**Function**
Resists nutation; separates greater from lesser sciatic foramen

**Tight in**
Sacral nutation

## Relations

**In front**
[Coccygeus muscle](https://durgical.com/en/anatomy/coccygeus-muscle/) and the pelvic cavity

**Behind**
[Sacrotuberous ligament](https://durgical.com/en/anatomy/sacrotuberous-ligament/)

**Above**
Greater sciatic foramen with [piriformis](https://durgical.com/en/anatomy/piriformis-muscle/), the [sciatic nerve](https://durgical.com/en/anatomy/sciatic-nerve/) and the gluteal vessels

**Below**
Lesser sciatic foramen with the [obturator internus tendon](https://durgical.com/en/anatomy/tendon-of-obturator-internus/)

## How to find it

On vaginal or rectal examination the ischial spine is felt on the side wall, and the ligament as a firm band running from it back toward the sacrum.

## On imaging

Not seen on radiographs; its bony anchor, the ischial spine, is. On MRI and CT it is a thin dark band from the ischial spine to the side of the lower sacrum and coccyx, with the coccygeus on its pelvic side. Its main imaging use is as a target: CT or ultrasound guides a pudendal nerve block at the ischial spine, just behind the ligament.

## Clinical notes

- Sacrospinous fixation for vaginal vault prolapse: sutures are placed medial to the ischial spine to spare the pudendal nerve and vessels
- Pudendal nerve entrapment can occur where the nerve crosses this ligament
- Bleeding from the inferior gluteal or internal pudendal vessels, which run close behind the ligament near the ischial spine, is a recognised complication of sacrospinous fixation

## Memory aid

PIN crosses the ischial spine: Pudendal nerve, Internal pudendal vessels, Nerve to obturator internus.

## Test yourself

Think of the answer, then tap the question to see it.

## Which structures cross behind the sacrospinous ligament at the ischial spine?

The pudendal nerve, internal pudendal vessels and nerve to obturator internus (PIN), leaving the greater and entering the lesser sciatic foramen.

## Which two foramina does the sacrospinous ligament separate?

The greater sciatic foramen above from the lesser sciatic foramen below.

## In sacrospinous fixation for vaginal vault prolapse, why are sutures placed medial to the ischial spine?

To spare the pudendal nerve and vessels, which cross at the ischial spine.

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Educational information, not medical advice. For any symptom, see a health professional.

## Its names

**Official Latin (TA2)**
ligamentum sacrospinale TA2 1852

**Official Spanish (DeCS)**
Ligamento sacroespinoso

**English (TA2)**
Sacrospinous ligament

**Also called**
sacrospinal ligament · ligamentum sacrospinosum

## Related

- [Sacrotuberous ligament](https://durgical.com/en/anatomy/sacrotuberous-ligament/)
- [Sacrum](https://durgical.com/en/anatomy/sacrum/)
- [Hip bone](https://durgical.com/en/anatomy/hip-bone/)

Sources: Terminologia Anatomica (TA2); [Anatomy, Bony Pelvis and Lower Limb: Pelvic Joints](https://www.ncbi.nlm.nih.gov/books/NBK538523/); [Anatomy, Abdomen and Pelvis: Ligaments](https://www.ncbi.nlm.nih.gov/books/NBK493215/).

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Representative model, for educational purposes only.

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Source: https://durgical.com/en/anatomy/sacrospinous-ligament/
License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/anatomy/sacrospinous-ligament/