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Posterior talofibular ligament

The posterior talofibular ligament (PTFL) is the strongest and most horizontally oriented component of the lateral collateral ligament complex of the ankle, along with the anterior talofibular ligament (ATFL) and calcaneofibular ligament (CFL). It stabilizes the ankle during dorsiflexion and prevents excessive posterior displacement of the talus.

PTFL injuries are less common than ATFL or CFL tears, as it is more robust and usually damaged only in severe ankle sprains, dislocations, or fractures. It plays a crucial role in ankle stability, especially in high-grade inversion injuries.

Synonyms

  • PTFL

  • Posterior fibulotalar ligament

  • Posterior ankle lateral ligament

Origin, Course, and Insertion

  • Origin: Posterior border of the lateral malleolus of the fibula

  • Course: Runs almost horizontally posteriorly and medially across the ankle joint

  • Insertion: Lateral tubercle of the posterior process of the talus (sometimes extending to posterior intermalleolar ligament fibers)

Relations

  • Superiorly: Posterior aspect of the distal fibula and peroneal tendons

  • Inferiorly: Posterior subtalar joint capsule

  • Anteriorly: Posterior ankle joint capsule and talus

  • Posteriorly: Achilles tendon and flexor hallucis longus tendon

Function

  • Stabilization: Provides strong restraint against posterior displacement of the talus

  • Support in dorsiflexion: Tightens during ankle dorsiflexion to prevent excessive rotation

  • Part of lateral ankle complex: Works with ATFL and CFL to resist inversion and rotational forces

  • Secondary stabilizer: Protects against talar external rotation during high-load movements

Clinical Significance

  • Injury mechanism: Usually torn in severe inversion sprains, subtalar dislocations, or fracture-dislocations of the ankle

  • Frequency: Less commonly injured than ATFL or CFL due to strong fiber orientation

  • Symptoms of tear: Posterior ankle pain, swelling, instability, tenderness over fibular posterior edge

  • Chronic instability: PTFL insufficiency contributes to recurrent ankle instability and degenerative changes

  • Surgical importance: Reconstructed in cases of lateral ligament reconstruction for severe ankle instability

MRI Appearance

  • T1-weighted images:

    • Normal PTFL: low signal intensity (dark band) running horizontally from fibula to talus

    • Surrounding fat: bright, providing good contrast

    • Tear: discontinuity or irregular contour with intermediate-to-bright signal

  • T2-weighted images:

    • Normal PTFL: low signal (dark), appears thinner than ATFL but denser

    • Partial tear: focal bright hyperintense signal within fibers

    • Complete tear: discontinuity, surrounding edema, and possible joint effusion

  • STIR:

    • Normal: low signal band

    • Pathology: bright hyperintense thickening or gap, better for detecting edema, hemorrhage, or fluid around ligament

  • Proton Density Fat-Saturated (PD FS):

    • Normal: sharply marginated, dark, continuous band

    • Tears: bright linear signal changes or fiber discontinuity

    • Excellent for subtle partial-thickness tears

  • T1 Fat-Sat Post-Contrast:

    • Normal: minimal to no enhancement

    • Pathology: enhancement along torn fibers or adjacent capsule in acute or healing phases

CT Appearance

Non-Contrast CT:

  • Ligament not directly visualized due to soft-tissue density

  • Indirect signs: avulsion fractures of posterior fibula or talus

  • May show joint effusion or adjacent bony injury

Post-Contrast CT (standard):

  • Ligament poorly delineated

  • Adjacent soft-tissue thickening or hematoma may be inferred

MRI image

Posterior talofibular ligament axial cross sectional anatomy 3T MRI AI enhanced radiology image-img-00000-00000

MRI image

Posterior talofibular ligament coronal cross sectional anatomy 3T MRI AI enhanced radiology image-img-00000-00000

CT image

Posterior talofibular ligament ct axial