Tap, joint (aspiration): A procedure whereby a sterile needle and syringe are used to drain joint fluid from the joint. This is usually done as an office procedure or at the bedside in the hospital. The skin over the joint is sterilized with a liquid. Local anesthetic is applied to the area of the joint either by injection or topical liquid freezing, or both. A needle with a syringe attached is inserted within the joint and fluid is sucked back (aspirated). For certain conditions medication is put into the joint after fluid removal. The needle is then removed and a bandaid or dressing is applied over the entry point.
Joint fluid is typically sent for examination to the lab to determine the cause of the joint swelling, such as infection, gout, and rheumatoid disease. Arthrocentesis can be helpful in relieving joint swelling and pain.