Kager fat pad (also known as the pre-calcaneal fat pad or pre-Achilles 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.
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, ankylosis spondylitis, reactive arthritis)
- adjacent neoplasm (soft tissue, osseous)
In the setting of trauma, oedema in Kager's 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.
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- 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.