Is Fluid Normal in Joints?
A small amount of fluid exists in normal joints. When a joint is affected by arthritis, particularly an inflammatory arthritis such as rheumatoid arthritis (RA), increased abnormal amounts of fluid build up, the knee appears swollen. The fluid is produced by the tissues that are affected by the arthritis and that line the joint.
Why Drain Fluid From a Joint?
Often, your doctor will drain the fluid from a large joint such as the knee to help relieve the pressure in the joint, thereby helping with symptoms. In addition, if infection is not suspected, they may elect to inject a small amount of cortisone in the knee to help prevent the fluid from returning.
Why Is the Fluid Tested? What Does It Show?
Studying the removed fluid can help with diagnosis. For example, if the patient has a warm and red knee, there is a chance that the joint is infected. Sending the fluid off to the lab for culture can help confirm or rule out an infection. In addition, a blood count on the fluid can be obtained. If there are a lot of white blood cells in the specimen, the fluid may be cloudy. Cloudy fluid can be seen in patients with infection, rheumatoid arthritis, and gout.
In addition, gout fluid may have a golden color. In patients with osteoarthritis, the fluid is often clear. Finally, in patients who have injured their knee, the fluid may be clear or bloody.
Dr. Zashin is clinical assistant professor at University of Texas Southwestern Medical School and an attending physician at Presbyterian Hospitals of Dallas and Plano. Dr. Zashin is author of Arthritis Without Pain - The Miracle Of TNF Blockers. The book is useful for anyone on one of the biologic drugs or considering the biologic drugs.
