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Posterior malleolus

The posterior malleolus is the posterior bony projection of the distal tibia forming the posterior margin of the ankle mortise. It contributes to the articular surface of the ankle joint and plays a key role in the stability of the tibiotalar joint and the posterior tibiofibular syndesmosis.

It is a critical structure in ankle anatomy and imaging, particularly in the assessment of ankle trauma and syndesmotic integrity.

Synonyms

  • Posterior tibial malleolus

  • Posterior tibial lip

Location

  • Situated at the distal end of the tibia

  • Forms the posterior margin of the ankle mortise

  • Posterior to the tibial plafond

  • Medial to the distal fibula

  • Superior to the talar dome

  • Part of the distal tibiofibular syndesmosis complex

Anatomical components

  • Osseous projection of the distal tibia

  • Articular surface:

    • Contributes to the tibial surface articulating with the talus

  • Ligamentous attachments:

    • Posterior inferior tibiofibular ligament (PITFL)

    • Posterior transverse tibiofibular ligament

  • Capsular attachments:

    • Posterior ankle joint capsule

Relations

Anteriorly:

  • Tibial plafond

  • Ankle joint cavity

Posteriorly:

  • Posterior ankle soft tissues

  • Flexor hallucis longus tendon (nearby)

Medially:

  • Medial malleolus

  • Deltoid ligament complex (posterior fibers)

Laterally:

  • Distal fibula

  • Posterior tibiofibular syndesmosis

Inferiorly:

  • Talus (posterior talar dome)

Superiorly:

  • Distal tibial metaphysis

X-ray appearance

Plain radiographs (AP, lateral, and mortise views):

  • Posterior malleolus: Seen best on lateral view as a posterior bony projection of the distal tibia

  • Cortical outline: Smooth and continuous

  • Articular surface: Forms part of the posterior ankle joint margin

  • Mortise view: Posterior margin may be partially visualized

CT appearance (Pre-contrast)

Non-contrast CT:

  • Posterior malleolus: Clearly defined posterior bony lip of the distal tibia

  • Cortical margins: Sharp and well delineated

  • Trabecular pattern: Normal cancellous bone

  • Articular contour: Smooth surface articulating with talus

  • Syndesmotic relationship: Accurately assessed in axial and sagittal planes

MRI appearance

T1-weighted images:

  • Cortical bone: Low signal intensity

  • Marrow of posterior malleolus: High signal intensity

  • Articular cartilage: Thin intermediate signal layer

  • Adjacent ligaments: Low-signal linear structures

T2-weighted images:

  • Cortical margins: Low signal

  • Joint fluid: High signal outlining the posterior joint recess

  • Cartilage: Intermediate-to-high signal

  • Posterior inferior tibiofibular ligament: Low-signal band

STIR:

  • Bone marrow: Uniform fat-suppressed signal

  • Posterior joint recess: Bright fluid signal

  • Ligaments and cortex: Remain low signal

Proton density fat-saturated (PD FS):

  • Bone marrow: Fat signal suppressed

  • Joint fluid: Bright high signal

  • Ligaments and cartilage: Clearly differentiated

CT VRT 3D image

Posterior malleolus 3d

MRI image

Posterior malleolus mri anatomy labelled image-img-00000-00000

CT image

Posterior malleolus ct sag image