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# Obturator externus tendon

The obturator externus tendon winds under the femoral neck and attaches in a pit at the back of the top of the [femur](https://durgical.com/en/anatomy/femur/).

Official name: Tendon of obturator externus

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## What it is

The tendon of the [obturator externus](https://durgical.com/en/anatomy/obturator-externus/), attaching in a pit at the back of the femoral neck (trochanteric fossa).

## What it does

Carries the pull of the obturator externus to turn the thigh outward.

## Key points

- The deep branch of the medial circumflex femoral artery passes behind this tendon and in front of the [obturator internus](https://durgical.com/en/anatomy/obturator-internus/) and gemelli on its way to the femoral head; the tendon is the landmark that keeps it safe
- Unlike the other short lateral rotators, it belongs to the medial (adductor) group and is supplied by the [obturator nerve](https://durgical.com/en/anatomy/obturator-nerve/)
- Its insertion, the trochanteric fossa, is the usual entry point for straight femoral nails, often loosely called the [piriformis](https://durgical.com/en/anatomy/piriformis-muscle/) fossa (texts differ on the name)

## Key facts

**Attaches**
Runs below and behind the femoral neck to the trochanteric fossa

**Function**
Lateral rotation of the thigh; steadies the femoral head; the deep branch of the medial circumflex femoral artery, the main supply of the femoral head, runs beside it, so hip surgeons preserve it

**Tight in**
Hip medial rotation

## Relations

**Course**
From the outer surface of the [obturator membrane](https://durgical.com/en/anatomy/obturator-membrane/) and the bone around it, it passes below the hip joint, then curves back under the femoral neck to the trochanteric fossa

**Above**
Lower [hip capsule](https://durgical.com/en/anatomy/articular-capsule-of-hip-joint/) and the back of the femoral neck

**Behind**
Deep branch of the [medial circumflex femoral artery](https://durgical.com/en/anatomy/medial-circumflex-femoral-artery/), then the [inferior gemellus](https://durgical.com/en/anatomy/inferior-gemellus-muscle/) and the [quadratus femoris](https://durgical.com/en/anatomy/quadratus-femoris-muscle/)

## How to find it

Not palpable; at operation it is found deep and below the gemelli and the quadratus femoris, curving behind the femoral neck to the trochanteric fossa.

## On imaging

On MRI it is seen as a tendon curving under and behind the femoral neck; muscle oedema or strain is an uncommon cause of deep groin pain in athletes.

## Clinical notes

- In surgical hip dislocation through a trochanteric osteotomy, the obturator externus is left intact to protect the medial circumflex femoral artery
- Strains of the obturator externus are uncommon causes of deep groin pain in sports with twisting, and are seen on MRI

## Test yourself

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

## Where does the obturator externus tendon insert?

In the trochanteric fossa, after running below and behind the femoral neck.

## Why do hip surgeons preserve the obturator externus tendon?

The deep branch of the medial circumflex femoral artery, the main supply of the femoral head, passes behind it.

## Which nerve supplies the obturator externus, unlike the other short lateral rotators?

The obturator nerve; it belongs to the medial (adductor) group.

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## Its names

**Official Latin (TA2)**
obturator externus TA2 2636

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

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

**Also called**
obturator externus muscle

## Related

- [Obturator externus](https://durgical.com/en/anatomy/obturator-externus/)
- [Femur](https://durgical.com/en/anatomy/femur/)

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/); [Anatomy, Bony Pelvis and Lower Limb: Medial Thigh Muscles](https://www.ncbi.nlm.nih.gov/books/NBK534775/).

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Representative model, for educational purposes only.

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Source: https://durgical.com/en/anatomy/tendon-of-obturator-externus/
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-externus/