"Kager fat pad, also known as the 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."
"haemorrhage (e.g. Achilles tendon tear)"
"infection (e.g. soft tissue, osteomyelitis)"
"inflammation (e.g. retrocalcaneal bursitis, peritendinitis)"