Also known as preachillis bursitis
Located between tendo achillis and calcaneus
Associated with RA, AS, psoriasis, Reiter's syndrome; and also achillis tendinitis.
Plain radiograph:
Absent lucency in posteroinferior corner of Kager's fat
Erosion of calcaneus
MRI:
STIR or FS T2 shows fluid in the bursa
Bursa larger than 1 mm in AP, 7 mm in sag, or 11 mm transversely is considered abnormal
References:
1. Ly JQ et al. Anatomy of and Abnormalities Associated with Kager's Fat Pad . AJR 2004; 182:147-154
2. Bottger BA, Schweitzer ME, El-Noueam KI, Desai M. MR imaging of the normal and abnormal retrocalcaneal bursae. AJR Am J Roentgenol 1998; 170:1239-1241
