Test Overview

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

Normally, only a
small amount of joint fluid is found in a joint. Joint fluid acts as a
lubricant for the joint and cushions joint structures. If you have a joint
problem, you may have more fluid in your joint and your joint may become
swollen, stiff, and painful.

A sample of joint fluid can be taken
from any joint in your body. The joint fluid is then analyzed in a lab to look
for inflammation, infection, gout, pseudogout, or bleeding.

Why It Is Done

Joint fluid analysis 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 To Prepare

Tell your doctor if you:

  • Have had bleeding problems, or take a blood thinner, such as aspirin, clopidogrel (Plavix), or warfarin (Coumadin), or take over-the-counter medicines, such as ibuprofen (Advil, Motrin) or naproxen (Aleve). Your doctor will tell you when you should stop taking these medicines several days before your procedure. Make sure that you understand exactly what he or she wants you to do.
  • Are allergic to any medicines, including
    anesthetics.
  • Are or might
    be pregnant.

Talk to your doctor about any concerns you have about the
need for the test, its risks, how it will be done, or what the results will
mean. To help you understand the importance of this test, fill out the
medical test information form (What is a PDF document?).

How It Is Done

Joint fluid analysis takes about 20
minutes and can be done in your doctor’s office, clinic, operating room, or
emergency room. Depending on which joint will be examined, you may be asked to
undress and put on a hospital gown. You will sit or lie down on an examining
table.

Your doctor will examine the joint to determine where the
needle should be inserted. The skin over the joint area will be cleaned with
antiseptic solution. A
local anesthetic is often injected into the skin over
the joint. For young children, a
sedative may also be given.

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.

Risks

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.

Results

Joint fluid analysis is a test to look
at joint fluid under a microscope for problems such as infection,
gout,
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

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 in the joint fluid that are causing an infection may be seen under a
    microscope after being colored with a Gram stain (a special dye). Joint fluid added to a substance that promotes the growth of germs (such as bacteria or a fungus) may show an infection. This is called a culture.

What Affects the Test

You may not be able to have
this test or the results may not be useful if:

  • You do not have enough fluid in the joint space.
  • You have recently had cortisone injected into the same
    joint.
  • You have an
    infection in the skin near the joint.

What To Think About

  • Your doctor may recommend further treatment
    with medicine, physical therapy, or surgery after the cause of your joint pain
    has been found.
  • Tissue from the joint lining may be removed during
    this test (synovial biopsy). The tissue sample is then examined under a
    microscope.

References

Other Works Consulted

  • Pagana KD, Pagana TJ (2010). Mosby’s Manual of Diagnostic and Laboratory Tests, 4th ed. St. Louis: Mosby Elsevier.

Credits

ByHealthwise Staff
Primary Medical Reviewer Anne C. Poinier, MD – Internal Medicine
E. Gregory Thompson, MD – Internal Medicine
Adam Husney, MD – Family Medicine
Martin J. Gabica, MD – Family Medicine

Current as ofOctober 10, 2017