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If a joint is filled with fluid, doctors may recommend arthrocentesis, which is also called joint aspiration or a joint tap. In this procedure, which can often be performed in a doctor’s office, fluid is removed from the joint. The principal goal of arthrocentesis can be to test the fluid to determine cause of swelling or the different kinds of conditions that may result in fluid build up. Alternately, the goal of joint aspiration can be to promote greater comfort in the patient by getting rid of painful swelling. In many cases, joint aspiration is performed for both diagnosis and pain relief.
As mentioned, arthrocentesis can take place in a doctor’s office. The area that will be tapped is usually cleaned with an antibacterial solution, and people are likely to have a local anesthetic, which will numb the particular joint from which fluid will be removed. Once the anesthetic is working, which takes a minute or two, a needle is injected into the joint and a small to greater amount of fluid is suctioned or aspirated from it. Usually the only post procedure necessity is applying a small bandage to the injection site.
Most people find arthrocentesis to be a relatively painless procedure because of the anesthetic used. If it feels painful, patients may want to ask doctors to stop. More local anesthetic may be needed.
Other people aren’t worried about discomfort but have trouble when they see aspiration needles, which can be on the large side. For those concerned about this issue, looking away while the procedure is performed is highly recommended. It should be noted that joint aspiration has a very low incidence of side effects, though in rare circumstances, infection of the joint occurs, especially if hygienic measures are not strictly observed.
Fluid that is collected can be sent to the lab for analysis and may be useful in differentiating between different types of arthritis that exist. Alternately, if something like infection is the cause of a joint swelling, examination of fluid collected by arthrocentesis can determine this too. Conditions a doctor might be looking for with joint aspiration include Lyme disease, gout, fungal infections, and presence of bleeding in joints.
The removal of fluid may also have a dual or other purpose. After arthrocentesis some people may feel much greater comfort. Fluid accumulation in a joint can result in painful swelling, and the removal of fluid could momentarily improve this condition, though build-up may occur again if the underlying cause isn’t addressed.
Arthrocentesis can be performed in virtually any joint. Common tap areas include joints in the hand, and especially the knee. The knee is particularly noted for its ability to collect fluid and may be one of the best sites to tap in order to determine if certain diseases are present.