Arthrocentesis (joint aspiration) is a procedure where a sterile needle and syringe are used to drain fluid from the joint, most often the knee.
During the procedure, the skin over the joint is sterilized using a liquid, typically iodine solution (Betadine) and local anesthetic (injection, topical liquid freezing, or both) is used in the area of the joint.
Then, a needle with a syringe attached is inserted within the joint a fluid is sucked back (aspirated) into the syringe. For certain conditions, the doctor will also inject medication into the joint after fluid removal (cortisone medications in order to rapidly relieve joint inflammation and further reduce symptoms). After the needle is then removed, a Band-Aid or dressing is applied over the entry point.
Analysis of joint fluid in the laboratory can help to define causes of joint swelling or arthritis, such as infection, gout, and rheumatoid disease. Also, joint fluid can be tested for white cell count, crystals, protein, glucose, as well as cultured to detect infection which can be helpful in defining the cause of a particular form of arthritis.
Arthrocentesis can also be helpful in relieving joint swelling and pain because removal of joint fluid that is inflamed can also remove the white blood cells within that are sources of enzymes that can be destructive to the joint.
The procedure is an office procedure or at the bedside of hospitalized patients. Minimal recovery time is required for this procedure. If the knee is aspirated, patients may wish to refrain from walking or standing for long periods at a time. The area will likely be tender for several days.