IS Case 140: Non-displaced fracture of the lateral tibial plateau
Imaging Sciences URMC 2008
Publication Date: 2009-05-21
Patient is a 28-year-old man involved in a motorcycle accident with injury to the left knee.
A lateral radiograph of the left knee demonstrates a small to moderate joint effusion, with a fat-fluid level. No definite fracture line is appreciated. CT imaging shows a small lipohemarthrosis and a non-displaced fracture of the lateral tibial plateau.
Subtle tibial plateau fractures are easily overlooked on radiographs. The only finding may be a lipohemarthrosis, which can be detected on the cross-table lateral radiograph. Kling described lipohemarthrosis of the knee in 1929. He found fat in the joint aspirate in 6 of 15 patients. In 1939 Holmgren first described the radiographic fat-fluid level following knee trauma by making lateral radiographs with a horizontal beam. It has been subsequently assumed that the observed fluid-fluid levels corresponded radiographically to marrow fat that was floating on blood. This notion has been subsequently challenged and it is proposed that a fluid-fluid level may also represent a simple hemarthrosis with separation of blood into serum and cellular elements. It has been proposed by Lugo-Olivieri, et al.  that a “double fluid-fluid” level (fat, serum, cellular components) is more specific for lipohemarthrosis. However, in general practice a fluid-fluid level has long been accepted as synonymous with lipohemarthrosis. Regardless, the presence of a fluid-fluid level indicates the need for a detailed radiologic search for a fracture, keeping in mind that a double fluid-fluid level may be a more specific finding.
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