This is a procedure to take joint fluid out of a joint using a sterile needle. This can be done in most of the joints in the body, but it is usually done on larger ones, such as the knee or shoulder.

Arthrocentesis
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Arthrocentesis is done to:

  • Find out why a joint is painful, swollen, or fluid-filled
  • Drain fluid out of a swollen joint to decrease pain and increase your ability to move the joint
  • Diagnose the specific type of arthritis occurring within a joint
  • Confirm a diagnosis of infection in the joint
  • Check for crystals in the joint fluid, which could be a sign of gout

In some cases, the doctor may inject medication into the joint space after the fluid has been taken out.