Synovial fluid analysis

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

How the Test is Performed

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 (fluid-filled sacs in the joints), and tendon sheaths.

After the joint area is cleaned, the health care provider inserts a sterile needle through the skin and into the joint space. Fluid is then drawn through the needle into a sterile syringe.

The fluid sample is sent to the laboratory. The laboratory technician:

• Checks the sample's color and how clear it is
• Places the sample under a microscope, counts the number of red and white blood cells, and looks for crystals (in the case of gout) or bacteria
• Measures glucose, proteins, uric acid, and lactate dehydrogenase (LDH)
• Cultures the fluid to see if any bacteria grow

How to Prepare for the Test

Normally, no special preparation is needed. Tell your provider if you are taking a blood thinner, such as aspirin, warfarin (Coumadin) or clopidogrel (Plavix). These medicines can affect test results or your ability to take the test.

How the Test will Feel

Sometimes, the provider will first inject numbing medicine into the skin with a small needle, which will sting. A larger needle is then used to draw out the synovial fluid.

This test may also cause some discomfort if the tip of the needle touches bone. The procedure usually lasts less than 1 to 2 minutes.

Why the Test is Performed

The test can help diagnose the cause of pain, redness, or swelling in joints.

Sometimes, removing the fluid can also help relieve joint pain.

This test may be used when your doctor suspects:

• Bleeding in the joint after a joint injury
• Gout and other types of arthritis

  Gout

  Gout is a type of arthritis. It occurs when uric acid builds up in blood and causes inflammation in the joints. Acute gout is a painful condition th...

  

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• Infection in a joint

What Abnormal Results Mean

Abnormal joint fluid may look cloudy or abnormally thick.

The following found in joint fluid can be a sign of a health problem:

• Blood -- injury in the joint or a body-wide bleeding problem
• Pus -- infection in the joint
• Too much joint fluid -- osteoarthritis or cartilage injury

Risks

Risks of this test include:

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

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 provider to determine what activity is most appropriate for you.