MedlinePlus Medical Encyclopedia: Culture

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Culture - joint fluid (aspirate)

Contents of this page:
Illustrations Alternative names Definition How the test is performed How to prepare for the test How the test will feel	Why the test is performed Normal Values What abnormal results mean What the risks are Special considerations

Illustrations

Joint aspiration

Alternative names Return to top

Joint fluid culture

Definition Return to top

Joint fluid culture is a laboratory test to isolate and identify organisms that cause infection, performed on a specimen of fluid obtained from fluid around a joint. See also synovial fluid analysis.

How the test is performed Return to top

A sample of joint aspirate or fluid is removed from the joint with a needle or in the operating room, then is placed on culture media in containers for the purpose of growing microorganisms (bacteria, fungus, or viruses) in the laboratory.

The microbiologist in the laboratory inspects the cultures daily for growth. If microorganisms are detected, other tests may be initiated to identify the infectious agent and determine the sensitivity of the organisms to medications. Antibiotic therapy can then be determined based on these results.

How to prepare for the test Return to top

A physician will withdraw fluid from a joint.

Infants and children:
The preparation you can provide for this test depends on your child's age, previous experiences, and level of trust. For general information regarding how you can prepare your child, see the following topics:

Infant test or procedure preparation (birth to 1 year)
Toddler test or procedure preparation (1 to 3 years)
Preschooler test or procedure preparation (3 to 6 years)
Schoolage test or procedure preparation (6 to 12 years)
Adolescent test or procedure preparation (12 to 18 years)

How the test will feel Return to top

The sample may be obtained in the health care provider's office or in the hospital. The skin over the joint is cleansed with antibacterial soap. A local anesthetic may be injected into the skin over the joint. The injection may burn or sting.

After the area has become numb, a larger needle is inserted into the joint, and fluid is withdrawn. There may be pressure in the joint. Some minor soreness may be present for several days.

Why the test is performed Return to top

The test may be performed when there is unexplained pain and inflammation of a joint, or suspected infection in a joint.

Normal Values Return to top

The presence of no organisms in the culture (a sterile culture) is normal.

What abnormal results mean Return to top

Abnormal results indicate an infection in the joint. The infection may be bacterial, mycobacterial, or fungal. The causative organism and an effective medication to treat the organism are often indicated in the final results.

Other associated conditions:

Fungal arthritis
Non-gonococcal (septic) bacterial arthritis
Gonococcal arthritis

What the risks are Return to top

The risks are introducing an infection or bleeding in the joint.

Special considerations Return to top

Not applicable.

Update Date: 1/26/2004

Updated by: Daniel Levy, M.D., Ph.D., Infectious Diseases, Greater Baltimore Medical Center, Baltimore, MD. Review provided by VeriMed Healthcare Network.

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