Calcaneofibular Ligament: Anatomy, Relations, Function, Clinical Significance, MRI & CT Imaging

Topic

Calcaneofibular ligament

The calcaneofibular ligament (CFL) is one of the three main components of the lateral collateral ligament complex of the ankle, along with the anterior talofibular ligament (ATFL) and the posterior talofibular ligament (PTFL). It is a strong, rounded cord that stabilizes the ankle against excessive inversion.

The CFL runs obliquely downward and posteriorly from the fibula to the calcaneus and is unique because it crosses both the ankle joint and the subtalar joint, contributing to stability in both. It is frequently injured in inversion ankle sprains, often in combination with the ATFL.

Synonyms

Fibulocalcaneal ligament
Lateral ankle calcaneal ligament

Origin, Course, and Insertion

Origin: Anterior border of the lateral malleolus of the fibula, just below the ATFL attachment
Course: Runs downward, backward, and slightly medially, crossing the peroneal tendons
Insertion: Lateral surface of the calcaneus, posterior to the peroneal tubercle

Relations

Anteriorly: Peroneal tendons (peroneus longus and brevis) run superficial to the ligament
Posteriorly: Posterior talofibular ligament and posterior ankle capsule
Superiorly: Lateral malleolus of fibula
Inferiorly: Lateral calcaneus near peroneal tubercle
Deep: Subtalar joint capsule

Function

Ankle stabilization: Restrains inversion of the ankle and subtalar joints
Subtalar stability: Only lateral ankle ligament that stabilizes both ankle and subtalar joints
Dynamic support: Works with ATFL to limit talar tilt
Injury prevention: Protects against varus stress and instability during walking and running

Clinical Significance

Ankle sprains: CFL commonly injured in inversion sprains, often with ATFL tear
Instability: Isolated CFL rupture or combined ATFL/CFL injury causes chronic lateral ankle instability
Examination: Pain and laxity on inversion stress test suggest CFL injury
Imaging relevance: MRI essential for confirming ligament continuity; ultrasound also used in dynamic assessment
Surgical role: Frequently reconstructed in ligament repair procedures for chronic ankle instability

MRI Appearance

T1-weighted images:
- Normal CFL: low signal (dark), thin cord-like structure
- Acute tear: discontinuity with intermediate-to-bright signal and surrounding edema
- Chronic tear: ligament thickening, irregular contour, or non-visualization
T2-weighted images:
- Normal ligament: low signal intensity (darker than on T1)
- Acute tear: bright hyperintense signal within or around ligament fibers
- Chronic injury: attenuation, thinning, or wavy ligament with associated joint fluid
STIR:
- Normal CFL: dark, sharply defined band
- Pathology: bright hyperintense signal in partial/complete tear, with edema in surrounding soft tissues
Proton Density Fat-Saturated (PD FS):
- Normal: compact, uniform low-signal ligament
- Partial tear: bright intraligamentous signal without complete discontinuity
- Complete rupture: gap or non-visualization with hyperintense fluid signal
T1 Fat-Sat Post-Contrast:
- Normal CFL: minimal or no enhancement
- Injured CFL: periligamentous or intraligamentous enhancement in cases of healing, scarring, or synovitis

CT Appearance

Non-Contrast CT:

CFL not well visualized directly due to its soft-tissue density
Indirect findings: lateral malleolar avulsion fractures or calcaneal avulsion fragments
Chronic pathology may show ossification or enthesophyte formation at attachment sites

Post-Contrast CT (standard):

Limited role; CFL itself does not enhance
Periligamentous enhancement may suggest inflammation or scarring

MRI images

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