Joint Fluid Analysis: About This Test

What is it?

For a joint fluid analysis, the doctor uses a needle to draw a small amount of fluid out of your joint so it can be looked at under a microscope. The test can be done in your doctor's office, a clinic, an operating room, or the emergency room.

Why is this test done?

This test is done to find inflammation, infection, gout, or pseudogout. Removing some of the joint fluid may also relieve pain caused by the buildup of fluid in your joint.

How do you prepare for the test?

• In general, you don't need to prepare before having this test. Your doctor may give you some specific instructions.
• If you take a medicine that prevents blood clots, your doctor may tell you to stop taking it before your test. Or your doctor may tell you to keep taking it. (These medicines include aspirin and other blood thinners.) Make sure that you understand exactly what your doctor wants you to do.

How is the test done?

• You will sit or lie down on an examining table.
• After the joint area is cleaned, a local anesthetic may be injected into your skin to numb the area.
• A long, thin needle is slowly inserted in the joint area. A syringe attached to the needle is used to remove a sample of joint fluid.
• A cortisone shot may be given into the joint before this needle is removed.
• A tight (pressure) bandage will be placed over the site to reduce swelling and bruising. An elastic bandage may also be wrapped around your joint, such as your knee, to reduce swelling.

How long does the test take?

• The test will take about 20 minutes.

What happens after the test?

• You will probably be able to go home right away.
• You can go back to your usual activities right away.
• The joint may be sore for 1 to 2 days after the test.
• If you have a cortisone shot, you may have some soreness or irritation at the site of the shot for 1 to 2 days.
• Avoid strenuous use of the joint for 2 to 3 days.

When should you call for help?

Call your doctor now or seek immediate medical care if:

• You have signs of infection, such as:
  • Increased pain, swelling, warmth, or redness.
  • Red streaks leading from the catheter site.
  • Pus draining from the catheter site.
  • A fever.