What is a synovial fluid analysis?

A synovial fluid analysis is a group of tests that looks for changes in your synovial fluid. These tests check for the cause of pain and swelling in your joints. Joints are places in the body where two bones meet, such as your knees, shoulders, hips, hands, and feet. Synovial fluid, also known as joint fluid, is a thick liquid located between your joints. The fluid cushions and protects the ends of bones and reduces friction during movement.

Normally, there is only a small amount of synovial fluid between the joints. If you have a joint problem, extra fluid can build up, causing pain, stiffness, and inflammation. Sometimes, removing the excess fluid is enough to reduce the pain you may have in the affected joint.

A synovial fluid analysis is a group of tests that checks for A synovial fluid analysis can help find out if you may have a disorder that affects the joints. The analysis usually includes:

• A check of the appearance of the synovial fluid, such as its color and thickness
• Chemical tests to check for changes in the synovial fluid's chemicals, such as glucose, protein acid, and uric acid
• Microscopic analysis to look for crystals, bacteria, and other substances

Other names: joint fluid analysis

What is it used for?

A synovial fluid analysis is used to help diagnose the cause of joint pain and inflammation. Inflammation is your body's response to injury or infection. It can cause pain, swelling, redness, and loss of function in the affected area. Causes of joint problems include:

• Osteoarthritis, the most common form of arthritis. This type of arthritis only affects the joints, usually in the hands, knees, hips, neck, and lower back. It's a chronic (long-lasting) disease that causes the joint cartilage to break down and become rough. It can be painful and lead to loss of mobility and function.
• Gout or calcium pyrophosphate deposition (pseudogout), types of inflammatory arthritis. They can cause pain, swelling, and redness in one or more joints. Having crystals in the synovial fluid may be a sign of these types of arthritis.
• Rheumatoid arthritis, a condition in which the body's immune system attacks healthy cells in your joints, causing pain, swelling, stiffness, and loss of function in your joints. It most commonly occurs in the wrist and fingers.
• Joint effusion, a condition that happens when too much fluid builds up around a joint. It often affects the knee. When it affects the knee, it may be referred to as knee effusion or fluid on the knee.
• Infection in a joint.
• A bleeding disorder, such as hemophilia. Hemophilia is a rare disorder in which the blood does not clot well. This can lead to sudden bleeding inside your body, such as in your joints, muscles, and organs. Sometimes the excess blood ends up in the synovial fluid.

Why do I need a synovial fluid analysis?

You may need this test if you have symptoms of a joint disorder. These include:

• Joint pain with a fever
• Joint swelling
• Redness over the joint
• A joint that feels warm to the touch
• Difficulty bending a joint

This test may also be used to monitor a known joint condition.

What happens during a synovial fluid analysis?

Your synovial fluid will be collected in a procedure called arthrocentesis, also known as joint aspiration. Your provider can then check the appearance, chemical properties, and what makes up your synovial fluid to check for any signs of infection or disease.

During the procedure:

• You will be asked to sit or lie down so your provider can access the affected joint.
• The provider will clean the skin on and around the affected joint.
• The provider will inject an anesthetic and/or apply a numbing cream to the skin. You shouldn't feel any pain during the procedure, but you may have some discomfort. If your child is getting the procedure, they may also be given a sedative. Sedatives are medicines that have a calming effect and help reduce anxiety.
• Once the needle is in place, your provider will withdraw a sample of synovial fluid and collect it in the syringe of the needle.
• Your provider will put a small bandage on the spot where the needle was inserted.

The procedure usually takes less than two minutes.

Will I need to do anything to prepare for the test?

You may need to fast (not eat or drink) for several hours before the test. Your provider will let you know if you need to fast and if there are any special instructions to follow.

Tell your provider if you are taking any blood thinner medicines.

Are there any risks to the test?

Your joint may be sore for a couple of days after the procedure. Your provider may ask that you limit your activity or recommend that you use ice packs or elevate the joint.

Serious complications, such as infection and bleeding may happen, but are uncommon. Let your provider know if you have increased redness, swelling, or pain at the joint.

What do the results mean?

Synovial fluid is usually light yellow, clear, and a little sticky or stringy. Abnormal synovial fluid may be cloudy and thicker or thinner than normal.

If your results show your synovial fluid was not normal, it may be a sign of one of the following conditions:

• A type of arthritis, such as osteoarthritis, rheumatoid arthritis, or gout
• A bleeding disorder
• A bacterial infection

Your specific results will depend on what abnormalities were found. If you have questions about your results, talk to your provider.

To understand the results of a synovial fluid analysis, your provider will consider your symptoms, medical history, and the results of other tests.

Learn more about laboratory tests, reference ranges, and understanding results.

Is there anything else I need to know about a synovial fluid analysis?

Arthrocentesis, the procedure used to do a synovial fluid analysis, may also be done to remove excess fluid from a joint. This procedure can help relieve pain and other symptoms.