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# Obturator internus tendon

The obturator internus tendon bends sharply around the [hip bone](https://durgical.com/en/anatomy/hip-bone/) as it leaves the [pelvis](https://durgical.com/en/anatomy/region/pelvis/) and attaches to the greater trochanter.

Official name: Tendon of obturator internus

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## What it is

The tendon of the obturator internus. It turns a sharp corner around the hip bone (the lesser sciatic notch) and joins the two gemelli to attach to the greater trochanter.

## What it does

Carries the pull of the obturator internus and gemelli to turn the thigh outward.

## Key points

- Shares the lesser sciatic foramen with the pudendal nerve, the internal pudendal vessels and the nerve to [obturator internus](https://durgical.com/en/anatomy/obturator-internus/), which turn here toward the perineum
- The sciatic nerve runs over the back of its tendon shared with the gemelli; in the posterior hip approach the tendon is detached and folded back over the nerve to shield it
- With the piriformis and gemelli it is reattached to the trochanter after a posterior hip replacement, which lowers dislocation rates

## Key facts

**Attaches**
Leaves the pelvis through the lesser sciatic foramen, turning about 90° over the lesser sciatic notch on a bursa; joined by the superior and inferior gemelli to the medial surface of the greater trochanter

**Function**
Lateral rotation of the extended hip and abduction of the flexed hip; holds the femoral head in the acetabulum

**Tight in**
Hip medial rotation

## Relations

**Superficial**
[Sciatic nerve](https://durgical.com/en/anatomy/sciatic-nerve/) and [gluteus maximus](https://durgical.com/en/anatomy/gluteus-maximus-muscle/)

**Above**
[Superior gemellus](https://durgical.com/en/anatomy/superior-gemellus-muscle/), then the [piriformis](https://durgical.com/en/anatomy/piriformis-muscle/)

**Below**
[Inferior gemellus](https://durgical.com/en/anatomy/inferior-gemellus-muscle/), then the [quadratus femoris](https://durgical.com/en/anatomy/quadratus-femoris-muscle/)

**Deep**
Back of the [hip capsule](https://durgical.com/en/anatomy/articular-capsule-of-hip-joint/) and the ischium

**Medial**
[Pudendal nerve](https://durgical.com/en/anatomy/pudendal-nerve/) and internal pudendal vessels in the lesser sciatic foramen

## How to find it

Not palpable; in the posterior approach it is found between the two gemelli, below the piriformis, as a flat shiny tendon; ultrasound shows it curving round the ischium.

## On imaging

On axial MRI it is seen bending round the lesser sciatic notch; fluid in its bursa there is an occasional finding, and oedema of the muscle can accompany deep buttock pain.

## Common problems

- Uncommonly, a source of deep buttock or pelvic pain when strained or tight.

## Clinical notes

- The obturator internus and gemelli can trap the sciatic nerve in deep gluteal syndrome
- Posterior hip dislocations often tear the short external rotators
- The pudendal (Alcock) canal is a sleeve in the fascia covering the obturator internus on the side wall of the ischioanal fossa; pudendal nerve entrapment there gives perineal pain that worsens on sitting

## Anatomical variants

- Its tendon joins the [piriformis tendon](https://durgical.com/en/anatomy/tendon-of-piriformis/) before inserting in about 1 in 10

## Test yourself

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

## Through which foramen does the obturator internus tendon leave the pelvis?

The lesser sciatic foramen, turning about 90° over the lesser sciatic notch on a bursa.

## Where does the obturator internus tendon insert?

With the superior and inferior gemelli, on the medial surface of the greater trochanter.

## How does the obturator internus tendon help protect the sciatic nerve in the posterior hip approach?

It is detached and folded back over the sciatic nerve to shield it.

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

## Its names

**Official Latin (TA2)**
obturator internus TA2 2605

**Official Spanish (DeCS)**
Tendón del obturador interno DeCS D013710

**English (TA2)**
Tendon of obturator internus

**Also called**
obturator internus muscle

## Related

- [Deep hip bursae](https://durgical.com/en/anatomy/bursa-of-piriformis-muscle/)
- [Obturator internus](https://durgical.com/en/anatomy/obturator-internus/)
- [Femur](https://durgical.com/en/anatomy/femur/)
- [Hip bone](https://durgical.com/en/anatomy/hip-bone/)

Sources: Terminologia Anatomica (TA2); [DeCS](https://decs.bvsalud.org/es/ths/resource/?id=14088); [Anatomy, Abdomen and Pelvis, Obturator Muscles](https://www.ncbi.nlm.nih.gov/books/NBK589636/).

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Representative model, for educational purposes only.

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