Fluid-fluid levels in injured knees: Do they always represent lipohemarthrosis?

Carlos H. Lugo-Olivieri, William W. Scott, Elias A. Zerhouni

Research output: Contribution to journalArticlepeer-review

23 Scopus citations


PURPOSE: To determine if fluid-fluid levels on horizontal-beam radiographs of posttraumatic knee joints always represent lipohemarthrosis. MATERIALS AND METHODS: The files of 41 patients with tibial plateau fracture were reviewed retrospectively. Twelve with fluid-fluid levels on radiographs who underwent computed tomography (CT) or magnetic resonance (MR) imaging were selected; CT attenuation and MR signal intensity patterns were used to assess fluid-fluid levels. Simulated hemarthrosis and lipohemarthrosis underwent plain radiography, CT, and MR imaging. RESULTS: Eight patients showed no evidence of fat in the supernatant fluid with either CT (n = 7) or CT and MR imaging (n = 1). Fluid levels resulted from blood separating into cellular elements and supernatant serum. Four patients showed evidence of lipohemarthrosis with either CT (n = 3) or MR imaging (n = 1); in one of these patients, a double fluid-fluid level could be demonstrated retrospectively on plain radiographs. CONCLUSION: Single fluid-fluid levels in posttraumatic knee joints do not necessarily represent a lipohemarthrosis. Double fluid-fluid levels are a more specific finding.

Original languageEnglish (US)
Pages (from-to)499-502
Number of pages4
Issue number2
StatePublished - Feb 1996


  • Joints, fluid
  • Joints, injuries
  • Knee, fractures

ASJC Scopus subject areas

  • Radiology Nuclear Medicine and imaging


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