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

The test can help diagnose the cause of pain or swelling in joints. Removing the fluid can also help relieve joint pain.

This test may be used to diagnose:

• Gout
• Infection
• Other inflammatory joint conditions
• Joint injury
• Osteoarthritis

A sample of synovial fluid is needed for this test. Synovial fluid is normally a thick, straw-colored liquid found in small amounts in joints, bursae, and tendon sheaths.

After the area is cleaned, the health care provider will insert a sterile needle through the skin and into the joint space. Once in the joint, fluid is drawn through the needle into a sterile syringe.

The fluid sample is sent to the laboratory. The laboratory technician will check the sample's color and clarity, and then place it under a microscope to check it for red and white blood 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.

Normally, no special preparation is necessary, but contact your health care provider before the test to make sure. Tell your doctor if you are taking blood thinners, as they can affect test results.

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.