When is joint aspiration necessary?
If a joint is swollen, analyzing a sample of joint fluid (synovial fluid) can help to find the cause of swelling. Even the color can be used as a first indication of what is wrong: Fluid from a healthy joint is usually clear. The fluid inside an injured joint is often a bloody reddish color, and the fluid inside an inflamed joint is usually cloudy. The sample of fluid can be tested to find out whether, for instance, it contains bacteria or abnormally high levels of white blood cells.
Aspiration may also be used as a treatment, to reduce the pressure on the joint, for example. Then the doctor uses the syringe to remove the excess fluid. If needed, medication can be injected into the joint during joint aspiration.
A contrast medium is sometimes injected into the area between the bones (the joint space) to make it easier to see details when taking an x-ray.