Fat droplets and synovial fluid leukocytosis in traumatic arthritis

The presence of fat droplets in synovial fluid signifies major or minor joint trauma with damage to the bones or adjacent supporting structures. Synovial fluids aspirated after traumatic hemorrhage usually have a low white blood cell count. In this report 2 patients with hemorrhagic effusions had synovial fluid leukocytosis, presumably secondary to lipid droplet phagocytosis. Lipid globules intra- and extracellulalary in the synovial fluid and a top fatty layer in the hematocrit spin of the hemorrhagic synovial fluid are indications of the traumatic etiology of this inflammatory arthritis.