Synovial fluid analysis is a group of tests that examine joint (synovial) fluid. The tests help diagnose and treat joint-related problems.

To obtain the fluid for analysis, a sterile needle is inserted into the joint space through skin that has been specially cleaned. Once in the joint, fluid is aspirated through the needle into a sterile syringe.

Synovial fluid is normally a viscous (thick), straw colored substance found in small amounts in joints, bursae, and tendon sheaths. In the laboratory, the fluid is initially analyzed for color and clarity. It is then examined microscopically for cells (red and white cells), crystals (in the case of gout), and bacteria. In addition, there may be a chemical analysis, and if infection is a concern, a sample will be cultured to see if any bacteria grow.

Abnormal joint fluid may look cloudy or abnormally thick.

Normally, no special preparation is necessary, but contact your health care provider before the test to make sure.

Occasionally, the health care provider will first inject local anesthesia with a small needle, which will sting. The aspiration is done with a larger needle and may also cause some pain. The procedure usually lasts less than one minute.