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Ency. home > Test > S > Synovial fluid analysis

Synovial fluid analysis   

Overview | Risks

Alternative names:

Joint fluid analysis; Joint fluid aspiration

Definition:

Synovial fluid analysis is a battery of tests performed on synovial (joint) fluid to help diagnose and treat joint-related abnormalities.

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 out.

Abnormal joint fluid may look cloudy or abnormally thick.

How to Prepare for the Test

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

Infants and children:
The physical and psychological preparation you can provide for this or any test or procedure depends on your child's age, interests, previous experience, and level of trust. For specific information regarding how you can prepare your child, see the following topics as they correspond to your child's age:

How the Test will Feel

Most health care providers will start by injecting local anesthesia with a small needle. This will sting transiently. The aspiration is done with a larger needle and may still be associated with some pain. The procedure usually lasts less than one minute.

Why the Test is Performed

The test is performed to diagnose the cause of pain or swelling in joints, and to relieve pain from fluid accumulation (usually blood or pus) in the joint. Common diseases diagnosed with fluid aspiration include infection, gout, and other inflammatory arthridities. Blood in the joint may be an indication of trauma inside the joint or a systemic bleeding problem.

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