Synovial fluid analysis

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Joint aspiration

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

Joint fluid analysis; Joint fluid aspiration

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

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

• Check the sample's color and clarity
• Place it under a microscope, count the number of red and white blood cells, and then look for crystals (in the case of gout) or bacteria
• Measure glucose, proteins, uric acid, and lactic dehydrogenase (LDH)
• Culture the fluid to see if any bacteria grow

Normally, no special preparation is needed. Tell your health care provider if you are taking blood thinners, because they can affect test results or your ability to take the test.

Sometimes, the health care provider will first inject numbing medicine into the skin with a small needle, which will sting. A larger needle will be used to draw out the joint fluid or synovial fluid.

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

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
• Infection in a joint

Review Date: 06/04/2011
Reviewed By: Linda J. Vorvick, MD, Medical Director, MEDEX Northwest Division of Physician Assistant Studies, University of Washington, School of Medicine; and C. Benjamin Ma, MD, Assistant Professor, Chief, Sports Medicine and Shoulder Service, UCSF Dept of Orthopaedic Surgery. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.

A.D.A.M., Inc. is accredited by URAC, also known as the American Accreditation HealthCare Commission (www.urac.org).