What Is Synovial (Joint) Fluid Analysis?

A synovial (joint) fluid analysis is a group of tests your doctor can use to diagnose problems with your joints.

Synovial fluid is the thick liquid that lubricates your joints and keeps them moving smoothly. It’s on all of your joints, including in your knees, shoulders, hips, hands, and feet.

Joint conditions like arthritis, gout, infections, and bleeding disorders can change how your synovial fluid looks and feels. A sample of this fluid taken during a procedure called an arthrocentesis can help your doctor figure out what’s causing your symptoms.

Why You Might Get This Test

If you have joint symptoms like:

  • Pain
  • Redness
  • Swelling
  • Fluid buildup

You may also get it so your doctor can figure out if you have:

Your doctor might also use this test to see if your treatment for your joint condition is working.

If your doctor thinks you need this test, ask them how to prepare. Let them know if you take blood thinners or any other medication.

What Happens During the Test

First, your doctor will give you a local anesthetic to numb your joint. Then, she'll put a needle in and take some fluid out. How much depends on the size of the joint and how many tests you're going to have.

Your doctor will send your fluid to a lab, where a technician will do one or more of these:

  • Check your fluid's color and thickness
  • Measure chemicals like glucose, protein, and uric acid
  • See how many red and white blood cells and crystals your fluid has
  • Test for bacteria, viruses, or other germs

What Your Results Mean

Normal synovial fluid is:

  • Clear
  • Colorless or pale yellow
  • Stringy
  • Free of bacteria, viruses, and fungi

Abnormal synovial fluid may be cloudy or thick.

A high white blood cell count can be from infection or another medical condition.

A high red blood cell count may happen when there is blood in the joint from an injury or bleeding disorder.

A high uric acid level and crystals can signal gout.

Ask your doctor what your results mean and how they might affect your treatment.

WebMD Medical Reference Reviewed by Laura J. Martin, MD on December 21, 2017

Sources

SOURCES:

Lab Tests Online: "Synovial Fluid Analysis."

Medscape: "Joint Fluid Interpretation."

National Institutes of Health: "Synovial Fluid."

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