Kager fat pad (also known as the precalcaneal fat pad or preAchilles fat pad) refers to the fat within the Kager triangle, which normally appears lucent (fat density) on radiographs and has relatively well-defined margins. Pathologies affecting nearby structures result in loss of the normal margins and increased density in the triangle.
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 4.
Normal appearance of Kager fat pad can be distorted by:
- infection (e.g. soft tissue, osteomyelitis)
- inflammation (e.g. retrocalcaneal bursitis, peritendinitis)
- thickened tendons (xanthomatosis, rheumatoid arthritis, gout, ankylosing spondylitis, reactive arthritis)
- adjacent neoplasm (soft tissue, osseous)
In the setting of trauma, edema in Kager fat pad should lead to a careful search for bony or soft tissue injury (i.e. Achilles tendon injury), perhaps requiring additional views and/or cross-sectional imaging depending on the clinical suspicion.
- 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. doi:10.2214/ajr.182.1.1820147 - 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. Goodman, L. R., and J. D. Shanser. "The pre-Achilles fat pad: An aid to early diagnosis of local or systemic disease." Skeletal Radiology 2, no. 2 (1977): 81-86.
- 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