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Superior peroneal retinaculum

The superior peroneal retinaculum (SPR) is a strong fibrous band located along the posterolateral aspect of the ankle. It plays a crucial role in stabilizing the peroneus longus and peroneus brevis tendons as they pass posterior to the lateral malleolus. The SPR forms part of the retinacular system of the ankle that maintains the tendons in their grooves during movement, preventing subluxation or dislocation.

It attaches superiorly to the lateral malleolus and inferiorly to the lateral calcaneal wall, blending with the deep fascia and the fibular periosteum. This structure is clinically important as injury or laxity of the SPR can result in peroneal tendon instability, a common cause of lateral ankle pain in athletes.

Synonyms

  • Superior fibular retinaculum

  • Lateral ankle retinaculum (superior portion)

  • Retinaculum musculorum peroneorum superius

Origin, Course, and Insertion

  • Origin: Posterolateral surface of the lateral malleolus and distal fibular periosteum

  • Course: Extends obliquely downward and posteriorly, forming a fibrous sheath over the peroneal tendons

  • Insertion: Lateral surface of the calcaneus and deep fascia of the leg

Relations

  • Anteriorly: Lateral malleolus and fibular periosteum

  • Posteriorly: Peroneal tendons and peroneal tendon sheath

  • Superiorly: Continuous with the deep fascia of the leg

  • Inferiorly: Blends with the inferior peroneal retinaculum and lateral calcaneal fascia

  • Medially: Fibular groove containing the peroneus longus and brevis tendons

  • Laterally: Subcutaneous tissue and skin overlying the ankle

Function

  • Tendon stabilization: Maintains the peroneus longus and brevis tendons within the retrofibular groove during ankle motion

  • Prevention of subluxation: Prevents tendons from slipping anteriorly over the lateral malleolus during dorsiflexion or eversion

  • Load transmission: Distributes tension between fibula and calcaneus

  • Joint support: Provides posterolateral stability to the ankle and subtalar joints

Clinical Significance

  • Tear or laxity: May cause peroneal tendon dislocation or instability, especially after ankle inversion injuries

  • Associated pathology: Common in athletes and dancers with repetitive ankle dorsiflexion-eversion movements

  • Chronic instability: Can lead to peroneal tendinopathy or longitudinal tendon splits

  • Symptoms: Posterolateral ankle pain, snapping or clicking sensation, tenderness behind the lateral malleolus

  • Imaging relevance: MRI and CT can directly visualize retinacular integrity and peroneal tendon position

MRI Appearance

  • T1-weighted images:

    • Normal SPR: low signal (dark fibrous band) overlying peroneal tendons

    • Adjacent muscle and fat planes: intermediate to bright

    • Tear or laxity: discontinuity or wavy contour of retinaculum with anterior tendon displacement

  • T2-weighted images:

    • Normal: dark linear structure superficial to peroneal tendons

    • Partial tear: focal bright hyperintensity or thickening

    • Complete tear: discontinuity with fluid signal beneath retinaculum

    • Tendon subluxation: peroneal tendons displaced anterior to fibula

  • STIR:

    • Normal: low signal

    • Pathology: bright hyperintense fluid outlining torn or elevated retinaculum

    • Excellent for detecting peroneal tendon sheath edema and acute injury

  • Proton Density Fat-Saturated (PD FS):

    • Normal: low-signal band superficial to tendons

    • Tear: bright signal gap or fluid accumulation between retinaculum and fibula

    • Chronic cases: thickened, irregular retinaculum with mild intermediate signal

  • T1 Fat-Sat Post-Contrast:

    • Normal: minimal enhancement

    • Acute tears or inflammation: enhancement along retinaculum margins

    • Chronic scarring: irregular enhancing band overlying tendons

CT Appearance

Non-Contrast CT:

  • Retinaculum seen as a thin soft-tissue density overlying the peroneal tendons

  • Avulsion fragments at fibular attachment may indicate acute injury

  • Peroneal groove morphology can be assessed for predisposing shallowness

Post-Contrast CT (standard):

  • Retinaculum shows mild homogeneous enhancement

  • Associated soft-tissue thickening or hematoma may be visible in acute cases

MRI image

Superior peroneal (fibular) retinaculum axial cross sectional anatomy 3T MRI AI enhanced radiology image-img-00000-00000

MRI image

Superior Peroneal Retinaculum axial cross sectional anatomy 3T MRI AI enhanced radiology image-img-00000-00000_00001

MRI image

Superior peroneal (fibular) retinaculum coronal cross sectional anatomy 3T MRI AI enhanced radiology image-img-00000-00000

CT image

Superior peroneal (fibular) retinaculum ct axial image