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# Fibular retinacula

The fibular retinacula are bands behind the outer ankle bone that keep the fibularis tendons in their groove.

Official name: Superior fibular retinaculum

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## What it is

Two bands behind and below the outer ankle bone.

## What it does

Keep the [fibularis longus](https://durgical.com/en/anatomy/fibularis-longus-muscle/) and brevis tendons in their groove behind the outer ankle bone.

## Key points

- The superior fibular retinaculum is the main restraint of the fibular tendons; it tears off the fibula with forced dorsiflexion and eversion while the fibularis muscles contract (skiing, football)
- Fleck sign: a thin bone flake off the lateral rim of the fibula on an ankle X-ray means the retinaculum has avulsed
- Under the inferior retinaculum, the fibular trochlea of the calcaneus separates the brevis tendon (above) from the longus tendon (below)

## Key facts

**Attaches**
Superior: lateral malleolus to calcaneus; inferior: lateral calcaneus (fibular trochlea), continuous with inferior extensor retinaculum

**Function**
Hold fibularis longus and brevis tendons behind lateral malleolus; superior tear lets them sublux

## Relations

**Contents**
Superior retinaculum: [fibularis brevis tendon](https://durgical.com/en/anatomy/tendon-of-fibularis-brevis/) (closer to the bone) and [fibularis longus tendon](https://durgical.com/en/anatomy/tendon-of-fibularis-longus/) (behind and outside it) in a common sheath; inferior retinaculum: the two tendons in separate sheaths

**Deep**
Retromalleolar groove of the [fibula](https://durgical.com/en/anatomy/fibula/), deepened by a fibrocartilage ridge, then the CFL and the lateral wall of the [calcaneus](https://durgical.com/en/anatomy/calcaneus/)

**Behind**
[Sural nerve](https://durgical.com/en/anatomy/sural-nerve/) and [small saphenous vein](https://durgical.com/en/anatomy/small-saphenous-vein/) running behind and below the lateral malleolus

**In front**
The inferior retinaculum continues into the stem of the inferior [extensor retinaculum](https://durgical.com/en/anatomy/extensor-retinaculum-of-the-wrist/)

## How to find it

Behind and below the lateral malleolus. When the foot everts and dorsiflexes against resistance, the tendons stand out in their groove; in instability they can be seen or felt snapping forward over the malleolus.

## Examination

- Resisted eversion and dorsiflexion from a plantarflexed, inverted start, with a finger on the groove: tendons slipping over the malleolus mean retinaculum failure
- Pressure on the groove during resisted eversion causing pain suggests a fibular tendon tear or tenosynovitis

## On imaging

AP or mortise X-ray shows the fleck sign; dynamic ultrasound shows the tendons subluxing in real time; MRI shows tendon splits, a shallow or convex groove, a low-lying brevis muscle belly or an extra muscle.

## Common problems

- Torn in some ankle injuries, letting the tendons slip out of the groove (subluxation), often with a snapping feeling. Surgery may be needed to repair it.

## Clinical notes

- Acute fibular tendon dislocation is often diagnosed as a lateral ankle sprain at first
- Eckert–Davis grades run from the retinaculum stripping the fibular periosteum (I) to a cortical bone avulsion (III)
- Calcaneal fractures with lateral wall blow-out can dislocate the fibular tendons and tear the retinacula
- Repair reattaches the retinaculum and may deepen the groove

## Anatomical variants

- An accessory fibularis quartus muscle or a low-lying [fibularis brevis](https://durgical.com/en/anatomy/fibularis-brevis-muscle/) belly can crowd the groove; the groove itself may be flat or convex instead of concave

## Test yourself

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

## What do the fibular retinacula hold, and which one is the main restraint?

The fibularis longus and brevis tendons behind the lateral malleolus; the superior fibular retinaculum is the main restraint.

## What mechanism tears the superior fibular retinaculum?

Forced dorsiflexion and eversion while the fibularis muscles contract, as in skiing or football.

## What does a fleck sign off the lateral rim of the fibula mean on an ankle X-ray?

Avulsion of the superior fibular retinaculum.

## Under the inferior fibular retinaculum, what separates the fibularis brevis from the fibularis longus tendon?

The fibular trochlea of the calcaneus: brevis above, longus below.

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

## Its names

**Official Latin (TA2)**
retinaculum fibulare superius; retinaculum fibulare inferius TA2 2715

**Official Spanish (DeCS)**
Retináculos fibulares superior e inferior

**English (TA2)**
Superior fibular retinaculum

**Also called**
superior peroneal retinaculum · inferior peroneal retinaculum · retinaculum proximale musculorum fibularium

## Related

- [Fibularis longus tendon](https://durgical.com/en/anatomy/tendon-of-fibularis-longus/)
- [Fibularis brevis tendon](https://durgical.com/en/anatomy/tendon-of-fibularis-brevis/)
- [Calcaneus](https://durgical.com/en/anatomy/calcaneus/)
- [Medial cuneiform](https://durgical.com/en/anatomy/medial-cuneiform-bone/)
- [Fifth metatarsal](https://durgical.com/en/anatomy/fifth/)
- [Tibia](https://durgical.com/en/anatomy/tibia/)

Sources: Terminologia Anatomica (TA2); [Anatomy, Bony Pelvis and Lower Limb: Leg Lateral Compartment](https://www.ncbi.nlm.nih.gov/books/NBK519526/).

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Representative model, for educational purposes only.

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