Synovial fluid analysis is utilized to diagnose the cause of pain, swelling, and fluid collection in the joints. The joints that are most commonly affected are the knee, hip, and shoulder joints. The conditions that affect the synovial fluid can be broken down into five general categories. These disease categories are Non-Inflammatory disease, Inflammatory disease, Infectious disease, Degenerative disease, and Bleeding disorders. Non-inflammatory diseases that are associated with synovial fluid involvement include trauma, sickle cell disease, and CPPD crystal deposition disease (pseudogout). Inflammatory diseases associated with synovial fluid include autoimmune disorders such as systemic lupus erythematosus, psoriasis, and rheumatoid arthritis as well as gout. Infectious arthritis is usually acute bacterial in nature. The most common causative organism in some studies is Neisseria gonnorrhea following by Staphylococcus aureus. Chronic septic arthritis is rare and reported causative organisms include Mycobacterium tuberculosis and Candida albicans. Bleeding disorders that lead to blood in the synovial fluid typically involve individuals with blood clotting disorders such as hemophilia, von Willenbrand’s disease, Glanzmann’s thrombasthenia, and synovial tumors as well as injuries. Degenerative disorders include primarily osteoarthritis which causes erosion of the joint surfaces and accumulation of fibrin.
The most important reason to perform an analysis on synovial fluid is to rule out septic arthritis. Analysis of synovial fluid is rarely needed in pediatric patients, but is used primarily to differentiate between inflammatory and non-inflammatory disease states. Analysis of synovial fluid usually includes multiple studies such as cell count, microscopic analysis, culture, examination for crystals, and other chemical analysis.