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Tarsal sinus

The tarsal sinus, also known as the sinus tarsi, is a cone-shaped, fat-filled space located on the lateral aspect of the hindfoot between the talus and calcaneus. It forms an important anatomical compartment within the subtalar joint complex and plays a key role in hindfoot stability and proprioception.

It is a critical landmark in foot and ankle anatomy, sports medicine, and cross-sectional imaging of the hindfoot.

Synonyms

  • Sinus tarsi

  • Tarsal sinus

Location

  • Situated on the lateral aspect of the hindfoot

  • Between the talus superiorly and the calcaneus inferiorly

  • Anterior to the posterior subtalar joint

  • Posterior to the talonavicular joint

  • Opens laterally to the skin surface of the foot

Anatomical components

  • Osseous boundaries:

    • Sulcus tali (on talus)

    • Sulcus calcanei (on calcaneus)

  • Contents:

    • Interosseous talocalcaneal ligament

    • Cervical ligament

    • Fat pad

    • Small vascular and neural structures

  • Articular relationships:

    • Part of the subtalar joint complex

Relations

Superiorly:

  • Neck of the talus

Inferiorly:

  • Anterior process of the calcaneus

Anteriorly:

  • Talonavicular joint

Posteriorly:

  • Posterior facet of the subtalar joint

Laterally:

  • Skin and subcutaneous tissues of the lateral foot

Medially:

  • Canalis tarsi (tarsal canal)

X-ray appearance

Plain radiographs (lateral and oblique foot views):

  • Tarsal sinus: Appears as a radiolucent space between talus and calcaneus

  • Best seen on: Lateral and oblique projections

  • Osseous margins: Smooth outlines of talus and calcaneus flanking the space

CT appearance

Non-contrast CT:

  • Tarsal sinus: Well-defined fat-density space between talus and calcaneus

  • Osseous margins: Sharp cortical outlines of sulcus tali and sulcus calcanei

  • Spatial detail: Excellent depiction of bony contours and sinus configuration

  • Contents: Fat and ligamentous structures inferred by density

MRI appearance

T1-weighted images:

  • Fat pad within sinus: High signal intensity

  • Ligaments: Low-signal linear structures traversing the space

  • Osseous margins: Low signal cortical bone

T2-weighted images:

  • Fat: Intermediate-to-high signal

  • Joint fluid: High signal if present within adjacent joints

  • Ligaments: Low signal against higher-signal fat and fluid

STIR:

  • Fat suppression: Marked suppression of sinus fat

  • Ligaments: Low signal bands become more conspicuous

  • Overall contrast: Excellent delineation of internal sinus architecture

Proton density fat-saturated (PD FS):

  • Fat pad: Suppressed signal

  • Ligaments: Clearly visualized as low-signal structures

  • Joint recesses: High signal

CT VRT 3D image

Tarsal sinus 3D

MRI image

Tarsal sinus mri anatomy labelled image-img-00000-00000

CT image

Tarsal sinus 3D