Synovial fluid analysis
What is this test?
This test detects characteristics of synovial fluid (fluid around the joints) such as the volume, color, or clarity. It is also used to measure biochemical parameters of synovial fluid such as the amount of glucose, uric acid, or total protein. This test is used to evaluate and manage joint diseases, such as suspected septic arthritis, gout or pseudogout, or inflammatory or non-inflammatory arthritis.
What are related tests?
Why do I need this test?
Laboratory tests may be done for many reasons. Tests are performed for routine health screenings or if a disease or toxicity is suspected. Lab tests may be used to determine if a medical condition is improving or worsening. Lab tests may also be used to measure the success or failure of a medication or treatment plan. Lab tests may be ordered for professional or legal reasons. You may need this test if you have:
- Brucella arthritis
- Septic arthritis
When and how often should I have this test?
When and how often laboratory tests are done may depend on many factors. The timing of laboratory tests may rely on the results or completion of other tests, procedures, or treatments. Lab tests may be performed immediately in an emergency, or tests may be delayed as a condition is treated or monitored. A test may be suggested or become necessary when certain signs or symptoms appear.
Due to changes in the way your body naturally functions through the course of a day, lab tests may need to be performed at a certain time of day. If you have prepared for a test by changing your food or fluid intake, lab tests may be timed in accordance with those changes. Timing of tests may be based on increased and decreased levels of medications, drugs or other substances in the body.
The age or gender of the person being tested may affect when and how often a lab test is required. Chronic or progressive conditions may need ongoing monitoring through the use of lab tests. Conditions that worsen and improve may also need frequent monitoring. Certain tests may be repeated to obtain a series of results, or tests may need to be repeated to confirm or disprove results. Timing and frequency of lab tests may vary if they are performed for professional or legal reasons.
How should I get ready for the test?
An arthrocentesis is a procedure that requires written consent. Review the consent form with the healthcare worker and ask any questions that you have before signing the consent form.
Tell the healthcare worker if you have a medical condition or are using a medication or supplement that causes excessive bleeding. You should also report if you have a history of allergic or other reactions to local anesthetics. Blood tests may need to be done before an arthrocentesis.
How is the test done?
Synovial fluid is the fluid around the joints. A synovial fluid sample is obtained by a procedure called an arthrocentesis. The skin over the joint will be cleaned, and a local anesthetic will be used to numb the tissue at the insertion site. A needle will be inserted into the space around the joint, and fluid collected into a syringe. After enough synovial fluid has been collected, the needle will be removed.
How will the test feel?
The amount of discomfort you feel will depend on many factors, including your sensitivity to pain. Communicate how you are feeling with the person doing the procedure. Inform the person doing the procedure if you feel that you cannot continue with the procedure.
During an arthrocentesis, a local anesthetic is given to numb the procedure area. You may feel mild discomfort or stinging when the numbing medicine is injected. You may feel pressure or discomfort during the procedure. Brief pain may be felt as the needle passes through the joint membrane. Your procedure site may be sore for several days.
What should I do after the test?
After an arthrocentesis is completed, pressure may be held to the site, and a bandage secured over the puncture site. If a large amount of fluid is removed, an elastic wrap may be used to support your joint. To treat swelling and pain, you may place cold packs over the joint. Avoid heavy use of the joint for a few days. If you have difficulty using the affected arm or leg after the procedure, contact your healthcare worker.
You will be given instructions for how to care for your bandage and the signs and symptoms of infection to watch for. Contact your healthcare worker if you have a fever or increased pain, and if you see increasing redness, swelling, or pus at the procedure site.
What are the risks?
Synovial fluid: An arthrocentesis is the procedure used to get a sample of synovial fluid for testing. Risks of an arthrocentesis include bleeding into the joint and joint infection. If you have a medical condition, or are using a medication or supplement that causes excessive bleeding, you are at a higher risk of bleeding from the puncture site. The person doing this procedure may need to perform it more than once. Talk to your healthcare worker if you have any concerns about the risks of having an arthrocentesis.
What are normal results for this test?
Laboratory test results may vary depending on your age, gender, health history, the method used for the test, and many other factors. If your results are different from the results suggested below, this may not mean that you have a disease. Contact your healthcare worker if you have any questions. The following are considered to be normal results for this test:
- Characteristics of Normal Synovial Fluid :
- Volume: Up to 3.5 mL
- Color: Pale yellow
- Clarity: Clear
- Viscosity: High (strings 3-6 mm long)
- Spontaneous clot formation: None
- Hyaluronate content: 3-4 g/L, decreases with age
- Cytologic examination:
- Erythrocytes: <2 x 109/L
- Leukocytes: <0.2 x 109/L
- Cytological sediment:
- Monocytes/macrophages: Approximately 60%
- Lymphocytes: Approximately 30%
- Neutrophilic granulocytes: Approximately 10% (<25%)
- Biochemical parameters:
- Glucose: Approximately same as plasma concentration (3.3-5.3 mmol/L)
- Uric acid: Identical to plasma concentration
- Total protein: 10-30 g/L
- Lactate: 1-1.8 mmol/L
- Lactate dehydrogenase: <4.8 microkatal/L
- Acid phosphatase: Negative
- Immunoglobulins: Approximately half of plasma concentration
- Rheumatoid factor: Negative
- Bacteria: Negative
- Crystals: Negative
- Fibrinogen: Negative
What follow up should I do after this test?
Ask your healthcare worker how you will be informed of the test results. You may be asked to call for results, schedule an appointment to discuss results, or notified of results by mail. Follow up care varies depending on many factors related to your test. Sometimes there is no follow up after you have been notified of test results. At other times follow up may be suggested or necessary. Some examples of follow up care include changes to medication or treatment plans, referral to a specialist, more or less frequent monitoring, and additional tests or procedures. Talk with your healthcare worker about any concerns or questions you have regarding follow up care or instructions.
Where can I get more information?
- Arthritis Foundation - http://www.arthritis.org
- National Institute of Arthritis and Musculoskeletal and Skin Disease - http://www.niams.nih.gov
- American Academy of Orthopaedic Surgeons - http://www.aaos.org/
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 Pascual E, Batlle-Gualda E, Martinez A, et al: Synovial fluid analysis for diagnosis of intercritical gout. Ann Intern Med 1999; 131:756-759.
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Last Updated: 8/4/2017