The double fat fluid level: lipohemarthrosis of the knee associated with suprapatellar plica synovialis.

Lipohemarthrosis is a frequent occurrence following intrarticular fracture. The contour of the fat and blood interface in the knee joint is dependent upon suprapatellar anatomy. Anatomic variations of the suprapatellar joint space can significantly alter the radiographic appearance of lipohemarthrosis. Three cases are presented in which a double fat-fluid level was identified, due to presence of a well developed suprapatellar plica synovialis. Recognition of the variable appearance of lipohemarthrosis of the knee is important to avoid overlooking this finding in the traumatized patient.