Synovial fluid analysis

Definition

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

Alternative Names

How the test is performed

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.

How to prepare for the test

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

How the test will feel

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.

Why the test is performed

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

What abnormal results mean

Blood in the joint may be a sign of injury inside the joint or a body-wide bleeding problem. An excess amount of normal synovial fluid can also be a sign of osteoarthritis.

What the risks are

• Infection of the joint -- unusual but more common with repeated aspirations
• Bleeding into the joint space

Special considerations

Ice or cold packs may be applied to the joint for 24 to 36 hours after the test to reduce the swelling and joint pain. Depending on the exact problem, you can probably resume your normal activities after the procedure. Talk to your health care provider to determine what activity is most appropriate for you.