Missed our latest free live-stream? Catch up now on our Procedure Tips (Chris Nicholas) and Right Lower Quadrant Pain (Matt Morgan)

C sign - talocalcaneal coalition

The C sign is an important radiological sign which may be seen on a lateral radiograph of the ankle in those with the talocalcaneal subtype of tarsal coalition. It can be seen in both osseous and non-osseous coalition.

Radiographic appearance

A continuous C-shaped arc on a lateral ankle radiograph is formed by the medial outline of the talar dome and posteroinferior aspect of the sustentaculum tali due to their bridging.

Differential diagnosis

Considerations include:

Inspired signs

Article information

rID: 25694
Section: Signs
Synonyms or Alternate Spellings:
  • C sign of tarsal coalition
  • C sign of talocalcaneal coalition
  • Calcaneal C sign

ADVERTISEMENT: Supporters see fewer/no ads

Cases and figures

  • Case 1: annotated image
    Drag here to reorder.
  • Case 2
    Drag here to reorder.
  • Case 3
    Drag here to reorder.
  • Case 4
    Drag here to reorder.
  • Case 5
    Drag here to reorder.
  • Updating… Please wait.

     Unable to process the form. Check for errors and try again.

     Thank you for updating your details.