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Joint Fluid Analysis

How It Is Done continued...

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. Samples of the fluid may be put in special tubes or containers and sent to the lab. A cortisone shot may be given into the joint before the needle is removed, to help keep fluid from building up again.

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 It Feels

You will feel a prick or sting when the anesthetic is given. You may feel tingling, pressure, pain, or fullness in your joint as the fluid is removed.


There is very little chance of having a problem after a joint fluid analysis. Infection, bleeding, or damage to the tendon, nerve, or joint is rare.

Sometimes your doctor may not be able to draw any fluid out. The joint space may be too small, you may have scar tissue in the joint space, or there may not be any fluid in the joint.

The joint may be sore for 1 to 2 days after the procedure. 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.


Joint fluid analysis is a test to look at joint fluid under a microscope for problems such as infection, gout camera.gif, pseudogout, inflammation, or bleeding. The test can help find the cause of joint pain or swelling.

The results of a joint fluid analysis are usually available the same day. The results from a culture are usually available in a few days.

Joint fluid analysis
  Normal Abnormal
Color and clarity

Clear to light yellow

Red (bloody) or milky white (cloudy)

Blood cell count

No large numbers of red or white blood cells

Large numbers of red or white blood cells

Crystals (seen under a special microscope with polarized light)

Not present


Gram stain and culture

No bacteria are seen and no organisms grow in the culture.

Bacteria are seen or organisms grow in the culture.

Abnormal values

  • Color and clarity. Slightly cloudy fluid may be caused by inflammation, gout, or pseudogout. A deep, dark red color may be caused by bleeding in the joint. Milky white may be caused by infection or inflammation.
  • Blood cell count. Large numbers of red blood cells may be caused by bleeding in the joint from injury, inflammation, or abnormal clotting of the blood. Large numbers of white blood cells may be caused by gout, pseudogout, other types of arthritis (such as rheumatoid arthritis), psoriatic arthritis, injury, or infection.
  • Presence of crystals. Uric acid crystals in the joint mean you have gout. Calcium pyrophosphate crystals mean you have pseudogout.
  • Gram stain and culture. Bacteria seen under a microscope on the Gram stain (a special dye) of the joint fluid may be caused by an infection. Bacteria that grows out of a culture plate in 1 to 2 days confirms the presence of an infection.

WebMD Medical Reference from Healthwise

Last Updated: June 04, 2012
This information is not intended to replace the advice of a doctor. Healthwise disclaims any liability for the decisions you make based on this information.

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