Joint fluid analysis; Joint fluid aspiration
Synovial fluid analysis is a group of tests that examine joint (synovial) fluid. The tests help diagnose and treat joint-related problems.
How the Test is Performed
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 joint area is cleaned, the health care provider inserts a sterile needle through the skin and into the joint space. Fluid is then drawn through the needle into a sterile syringe.
The fluid sample is sent to the laboratory. The laboratory technician:
- Checks the sample’s color and how clear it is
- Places the sample under a microscope, counts the number of red and white blood cells, and looks for crystals (in the case of gout) or bacteria
- Measures glucose, proteins, uric acid, and lactate dehydrogenase (LDH)
- Cultures the fluid to see if any bacteria grow
How to Prepare for the Test
Normally, no special preparation is needed. Tell your provider if you are taking a blood thinner, such as aspirin, warfarin (Coumadin) or clopidogrel (Plavix). These medicines can affect test results or your ability to take the test.
How the Test will Feel
Sometimes, the provider will first inject numbing medicine into the skin with a small needle, which will sting. A larger needle is then used to draw out the synovial fluid.
This test may also cause some discomfort if the tip of the needle touches bone. The procedure usually lasts less than 1 to 2 minutes.
Why the Test is Performed
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
What Abnormal Results Mean
Abnormal joint fluid may look cloudy or abnormally thick.
The following found in joint fluid can be a sign of a health problem:
- Blood — injury in the joint or a body-wide bleeding problem
- Pus — infection in the joint
- Too much joint fluid — osteoarthritis or cartilage injury
Risks
Risks of this test include:
- Infection of the joint — unusual, but more common with repeated aspirations
- Bleeding into the joint space
Considerations
Ice or cold packs may be applied to the joint for 24 to 36 hours after the test to reduce the swelling and joint pain. Depending on the exact problem, you can probably resume your normal activities after the procedure. Talk to your provider to determine what activity is most appropriate for you.
Synovial biopsy
Biopsy – synovial membrane; Rheumatoid arthritis – synovial biopsy; Gout – synovial biopsy; Joint infection – synovial biopsy; Synovitis – synovial biopsyA synovial biopsy is the removal of a piece of tissue lining a joint for examination. The tissue is called the synovial membrane.
How the Test is Performed
The test is done in the operating room, often during an arthroscopy. During this procedure:
- You will receive general anesthesia. This means you’ll be pain free and asleep during the procedure.
- The surgeon makes a tiny cut in the skin near the joint.
- An instrument called a trocar is inserted through the cut into the joint.
- A tiny camera with a light is used to look inside the joint.
- A tool called a biopsy grasper is then inserted through the trocar. The grasper is used to cut a small piece of tissue.
- The surgeon removes the grasper along with the tissue. The trocar and any other instruments are removed. The skin cut is closed and a bandage is applied.
- The sample is sent to a lab for examination.
How to Prepare for the Test
Follow your health care provider’s instructions on how to prepare. This may include not eating and drinking anything for several hours before the procedure.
How the Test will Feel
With the local anesthetic, you will feel a prick and a burning sensation. As the trocar is inserted, there will be some discomfort. If the surgery is performed under regional or general anesthesia, you will not feel the procedure.
Why the Test is Performed
Synovial biopsy helps diagnose gout and bacterial infections, or rule out other infections. It can be used to diagnose autoimmune disorders such as rheumatoid arthritis, or uncommon infections like tuberculosis.
Normal Results
The synovial membrane structure is normal.
What Abnormal Results Mean
Synovial biopsy may identify the following conditions:
- Chronic synovitis (inflammation of the synovial membrane)
- Coccidioidomycosis (a fungal infection)
- Fungal arthritis
- Gout
- Hemochromatosis (abnormal buildup of iron deposits)
- Systemic lupus erythematosus (autoimmune disease that affects the skin, joints, and other organs)
- Tuberculosis
- Synovial cancer (very rare type of soft tissue cancer)
- Rheumatoid arthritis
Risks
There is a very slight chance of infection and bleeding.
Considerations
Follow instructions for keeping the wound clean and dry until your provider says it is OK to get it wet.
