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.
- 1. Ly JQ, Bui-mansfield LT. Anatomy of and abnormalities associated with Kager's fat Pad. AJR Am J Roentgenol. 2004;182 (1): 147-54. AJR Am J Roentgenol (full text) - Pubmed citation
- 2. Theobald P, Bydder G, Dent C et-al. The functional anatomy of Kager's fat pad in relation to retrocalcaneal problems and other hindfoot disorders. J. Anat. 2006;208 (1): 91-7. doi:10.1111/j.1469-7580.2006.00510.x - Free text at pubmed - Pubmed citation
- 3. Wiegerinck JI, Somford MP, Hoornenborg D et-al. Eponyms of the Kager triangle. J Bone Joint Surg Am. 2012;94 (10): e67. doi:10.2106/JBJS.K.01074 - Pubmed citation
- 4. Somford MP, Hoornenborg D, Wiegerinck JJ. Kager's "Bermuda" Triangle. (2014) The Journal of foot and ankle surgery : official publication of the American College of Foot and Ankle Surgeons. 53 (4): 503-4. doi:10.1053/j.jfas.2014.02.002 - Pubmed