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Malleolar fossa

The malleolar fossa is a small but distinct depression located on the medial surface of the lateral malleolus of the fibula. It serves as an important attachment site for stabilizing ligaments of the ankle and forms a key anatomical landmark in the lateral compartment of the ankle joint.

It is of particular importance in ankle stability, trauma assessment, and detailed imaging evaluation of ligamentous attachments.

Synonyms

  • Fossa of the lateral malleolus

  • Fibular malleolar fossa

Location

  • Situated on the medial aspect of the lateral malleolus

  • At the distal end of the fibula

  • Posterior to the articular facet for the talus

  • Inferior to the fibular shaft

  • Within the lateral wall of the ankle mortise

Anatomical components

  • Osseous depression of the fibula

  • Cortical margins with underlying cancellous bone

  • Ligament attachment site:

    • Posterior talofibular ligament (PTFL)

  • Contributes to lateral ankle stability through ligament anchorage

Relations

Anteriorly:

  • Articular surface of the lateral malleolus for the talus

Posteriorly:

  • Posterior ankle capsule

Medially:

  • Talus

Laterally:

  • Subcutaneous tissue and skin

Inferiorly:

  • Distal tip of the lateral malleolus

Superiorly:

  • Distal fibular shaft

X-ray appearance

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

  • Malleolar fossa: Usually not distinctly visualized due to its small size

  • Inferred by: The contour of the lateral malleolus

  • Best appreciated: On oblique and mortise views as a subtle indentation

CT appearance

Non-contrast CT:

  • Malleolar fossa: Well-defined osseous depression on the medial surface of the lateral malleolus

  • Cortical margins: Sharp and smooth

  • Trabecular pattern: Normal cancellous bone

  • Spatial resolution: Excellent depiction of depth, contour, and orientation

  • Ligament attachment site: Inferred anatomically

MRI appearance

T1-weighted images:

  • Cortical bone: Low signal

  • Underlying marrow: High signal

  • Fossa contour: Clearly delineated

T2-weighted images:

  • Cortex: Low signal

  • Joint fluid: High signal outlining adjacent articular surfaces

  • PTFL: Seen as low-signal band inserting into the fossa

STIR:

  • Fat suppression: Uniform suppression of marrow fat

  • Fossa margins: Well visualized

  • Surrounding soft tissues: High contrast

Proton density fat-saturated (PD FS):

  • Bone marrow: Suppressed fat signal

  • Ligamentous structures: Clearly seen as low-signal bands

  • Joint fluid and synovium: High signal

CT VRT 3D image

Malleolar fossa 3d

MRI image

Malleolar fossa mri anatomy labelled image-img-00000-00000