What finding in the bloody synovial fluid may indicate that a fracture has caused the hemarthrosis?
A fracture may release blood and bone marrow elements including lipids into the synovial fluid. The synovial fluid may resemble “tomato soup”. The fat globules released from the bone marrow may be seen floating at the top of the synovial fluid by bedside visualization of the fluid in the syringe or collection tube. If there are fat globules present in the synovial fluid identified either by direct visualization or by oil red O staining, a fracture should be suspected. Subtle fractures through bony endplates adjacent to joints may be difficult to see on plain radiography, and computed tomography or magnetic resonance imaging (MRI) may be necessary to identify the fracture.
