Kager triangle

Kager triangle is a sharply marginated radiolucent triangle seen posteriorly on lateral radiographs of the ankle. It represents the Kager fat pad.

It is bordered anteriorly by the flexor hallucis longus (FHL) muscle and tendon, posteriorly by the Achilles tendon, and inferiorly by the calcaneus. The anteroinferior corner of the triangle is related to the posterior ankle joint, while posterolaterally it is related to the retrocalcaneal bursa

The alteration of it's radiographic appearance in the form of obliteration or distortion of its borders are subtle indicators of pathology involving the posterior ankle. 

History and etymology

Kager triangle and Kager fat pad were named after German orthopedic surgeon Hans Kager (1910-1941) 4 who described the anatomy of this region in an article on management of Achilles tendon tears in 1939. The first use of the term Kager triangle was not until 1958 3,4

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Article information

rID: 1544
Section: Anatomy
Tag: stub, cases
Synonyms or Alternate Spellings:
  • Kager triangle

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Cases and figures

  • Case 1: in black (also has a non-ossifying fibroma)
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