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Apex of lateral malleolus

The apex of the lateral malleolus refers to the most inferior and distal tip of the lateral malleolus of the fibula. It forms the prominent bony landmark on the lateral aspect of the ankle and plays a crucial role in stabilizing the ankle joint by providing attachment for key lateral ligamentous structures and contributing to the lateral boundary of the ankle mortise.

It is a key reference point in orthopedic anatomy, trauma assessment, ankle imaging, and surgical planning.

Synonyms

  • Tip of the lateral malleolus

  • Distal pole of the lateral malleolus

Location

  • Situated at the distal end of the fibula

  • Forms the lateral projection of the ankle joint

  • Inferior and posterior to the medial malleolus

  • Lateral to the talar dome

  • Superficial and subcutaneous on the lateral ankle

Anatomical components

  • Osseous projection of the fibula

  • Cortical shell with underlying cancellous bone

  • Ligament attachment zone:

    • Anterior talofibular ligament (ATFL)

    • Calcaneofibular ligament (CFL)

    • Posterior talofibular ligament (PTFL)

  • Articular relationship:

    • Contributes to the lateral wall of the ankle mortise

Relations

Anteriorly:

  • Anterior talofibular ligament

  • Anterolateral joint capsule

Posteriorly:

  • Posterior talofibular ligament

  • Peroneal tendons (posterior and inferior to the apex)

Medially:

  • Talar lateral articular surface

Laterally:

  • Subcutaneous tissue and skin

Inferiorly:

  • Lateral surface of the talus and calcaneus (via ligaments)

Superiorly:

  • Distal fibular shaft and metaphysis

X-ray appearance

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

  • Apex: Seen as the pointed distal tip of the lateral malleolus

  • Cortical outline: Sharp and well-defined

  • Relationship: Forms the lateral boundary of the ankle mortise

  • Best seen on: Mortise and AP views

CT appearance

Non-contrast CT:

  • Apex: Well-defined bony prominence at the distal fibula

  • Cortical margins: Smooth and sharply outlined

  • Trabecular pattern: Normal cancellous bone

  • Spatial assessment: Excellent for evaluating contour, orientation, and subtle cortical irregularities

  • Relationship to talus: Clearly demonstrated

MRI appearance

T1-weighted images:

  • Cortical bone: Low signal intensity

  • Marrow of lateral malleolus: High signal intensity

  • Apex contour: Clearly delineated against surrounding soft tissues

T2-weighted images:

  • Cortex: Low signal

  • Adjacent joint fluid: High signal outlining the apex

  • Surrounding ligaments and tendons: Low-to-intermediate signal

STIR:

  • Fat suppression: Uniform suppression of marrow fat

  • Apex margins: Well visualized

  • Joint and tendon sheaths: Bright signal

Proton density fat-saturated (PD FS):

  • Bone marrow: Suppressed fat signal

  • Joint fluid: High signal

  • ATFL and CFL fibers: Well seen as low-signal bands attaching near the apex

CT VRT 3D image

Apex of lateral malleolus 3d

MRI image

Apex of lateral malleolus mri anatomy labelled image-img-00000-00000

CT image

Apex of lateral malleolus ct