A 24-year-old woman presented with traumatic left wrist pain. X-rays were negative for fracture. Computed tomography (CT) showed hemorrhagic fatty effusions within the second and third wrist extensor tendon compartments (the “floating fat” sign) and a tiny cortical defect in the Lister's tubercle. Three weeks later, magnetic resonance imaging demonstrated a nondisplaced distal radius fracture with extensive marrow edema.
The floating fat sign within the extensor tendon compartments is a critical sign of a distal radius fracture, which can be occult on x-ray and CT.