Location

Multiple

Diagnosis

Aneurysmal bone cyst

Discussion

Single axial section of a knee CT which reveals an aneurysmal bone cyst in the left distal femur with a fluid-fluid level. The fluid-fluid level sign is by no means pathognomonic, but is helpful in narrowing the differential. The sign is produced by a cystic lesion with water density fluid layering atop blood. The fluid-fluid level is often seen in aneurysmal bone cysts, but it may also be seen in giant cell tumor, telangiectatic osteosarcoma, and chondroblastoma.

Reference

Davies AM, Cassar-Pullicino VN, Grimer RJ: The incidence and significance of fluid-fluid levels on computed tomography of osseous lesions. Br J Radiol 1992 Mar;65(771):193-8.

Figures

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Attachments:


kneectfluidlevel.jpg (image/jpeg)