Synovial fluid is a liquid found in small amounts within the joints. This liquid is produced by the membrane lining the capsule of a joint, known as the synovial membrane. During a joint aspiration, the synovial fluid is drawn out using a needle, and looked at under a microscope.

Who is a candidate for the test?

A joint aspiration is done to help diagnose joint problems in a person with joint pain, swelling, or deformity.

How is the test performed?

A joint aspiration can be done in a doctor's office. Local anesthesia is injected into the joint to numb the area. The area is then cleaned with an antiseptic. A sterile needle is inserted into the joint space. A small amount of the synovial fluid is withdrawn and sent to the laboratory for analysis.

The procedure usually takes about 10 minutes. The only discomfort usually occurs when the local anesthesia is injected.