ABSTRACT
Cytology of the musculoskeletal system can present unique challenges, in particular poor exfoliation of lesions or contamination of the sample with significant quantities of peripheral blood. However, cytology of joints, skeletal muscle, and bone can provide important diagnostic information. Synovial fluid should be collected into an ethylenediaminetetraacetic acid tube for cytologic analysis, a sterile glass tube for any serologic testing or culture, and/or a culturette for bacterial culture, if needed. Analysis of synovial fluid typically consists of measurement of the total protein concentration, a nucleated cell count, and cytologic assessment. Mononuclear inflammation of synovial fluid consists of increased numbers of large mononuclear cells, typically with a smaller fraction of small lymphocytes within the fluid. Hemarthrosis is hemorrhage within a synovial space, which may be seen secondary to trauma, anticoagulant rodenticide intoxication, hereditary coagulation abnormalities, and other bleeding diatheses. A varied population of cells makes up the synovial lining, including vascular and adipose tissue and cells of fibroblast and macrophage origin.
