Edematous processes within Kager fat pad: magnetic resonance imaging, gross anatomical, and histological studies in cadavers with clinical correlation.

Objective: To demonstrate the anatomical features of Kager fat pad (KFP) and its fasciae using magnetic resonance imaging, gross anatomy, and histology in cadavers; and to correlate the data with image findings in patients.

Methods: The KFP was analyzed in 10 fresh human cadavers and 152 clinical cases. The retrospective clinical study was institutional review board approved. The specimens were studied by magnetic resonance imaging and sectioned for anatomical/histological correlation. Clinical cases were selected to evaluate the frequency, distribution, and patterns of edema/inflammation in KFP. The square of the Pearson product moment correlation coefficient and Student t tests were performed.

Results: Fasciae about KFP are double layered and derived from the union of the fascia of the leg and flexor and peroneal retinacula. Edema in KFP could be divided into diffuse, confined anteriorly, confined posteriorly, and confined externally. Confined patterns of edema were associated with paratenonitis and fluid in the Achilles bursae (P < 0.05).

Conclusions: Four patterns of edema occur in KFP. Paratenonitis and bursal fluid were associated with confined edematous patterns. The double layer about KFP may contain edema that affects this region.