| Where It's Done | Who Does It | How Long It Takes | Discomfort/Pain |
| Hospital or doctor's office. | Doctor. | 3-5 minutes. | Minor discomfort associated with needle insertion. |
| Results Ready When | Special Equipment | Risks/Complications | Average Cost |
| 3-4 hours. | Syringe and needle, collecting tubes, and elastic wrap. | Infection (extremely rare if sterile conditions are strictly applied), bleeding or accumulation of blood, and joint pain. | $$ |
Joint tap, synovial fluid analysis, and closed joint aspiration.
Purpose- To establish the cause of joint swelling.
- To distinguish between different types of arthritis.
- To monitor the effects of antibiotic treatment on septic arthritis.
- As treatment, to drain excess fluid from a joint or to inject corticosteroids or other medications into the joint to relieve pain.
Synovial fluid (which helps lubricate the surface of bones and cartilage inside the joints) is withdrawn and analyzed in a laboratory for substances that may help establish the cause of joint swelling.
PreparationYou remove clothing as necessary to expose the joint.
Test procedure- The doctor examines your joint for excess fluid.
- The doctor marks the spot at which arthrocentesis will be performed, cleans the skin with an antiseptic liquid, and applies to the skin or injects a local anesthetic.
- A needle is inserted into the marked spot and guided into the joint space. You may feel a "pop" when it penetrates the joint capsule.
- After excess synovial fluid is removed, the needle is withdrawn and the fluid is sent to a lab for analysis.
- You will receive special instructions on joint care following arthrocentesis.
- In some cases, you may resume regular use of the joint immediately after the procedure, or you may be instructed to avoid excessive use of the joint.
- You may apply an ice pack to the joint if it is painful and swollen.
None.
InterpretationSynovial fluid that is opaque and turbid (instead of clear and viscous) may indicate inflammatory diseases, while the presence of pus may signal septic arthritis. Blood in the fluid may indicate a fracture or blood disorder, while crystals may signal gout or pseudogout. A high white blood cell count may indicate an inflammatory disorder. Various other tests, such as Gram stains for certain bacteria, cultures for infectious organisms, and glucose measurement, may be done if other problems are suspected.
Advantages- The test is indispensable for diagnosing septic arthritis and joint diseases associated with crystals.
- There is a low risk of complications.
None.
The next step- If blood is present, trauma or fracture may be diagnosed and an X-ray may be performed.
- If no blood is present, a culture and other tests may be performed.
Insertion of the needle is normally painless, although you may feel temporary pain when the joint capsule is penetrated. Let the doctor know if you experience persistent pain during arthrocentesis as this may mean that the cartilage or the membrane covering the bone is irritated. In this case, the doctor will usually withdraw the needle and insert it at a different angle.
