Extra-osseous fat fluid level: a specific sign for osteomyelitis

Osteomyelitis may pose as a diagnostic dilemma on various imaging modalities and may be confused with neoplasms and other pathology. Although a rare finding, extra-osseous fat fluid level, especially when associated with spongy bone destruction, can be considered a specific sign of osteomyelitis. Previously, only two cases of extra-osseous fat fluid level in osteomyelitis have been reported, one on computed tomography (CT) and the other on magnetic resonance imaging (MRI). The former was a case of septic arthritis with intra-articular fat fluid level. A case of osteomyelitis is presented with the demonstration of extra-osseous fat fluid level. Our case is unique in providing exquisite CT and MRI correlation.