A joint tap, often called joint aspiration, is a simple diagnostic procedure that a doctor uses to determine the cause of joint pain or other problems. Fluid is removed from the affected joint and sent to a laboratory for analysis. Doctors may use this procedure to complement other diagnostic tools, such as x-rays or bone scans. Minimal preparation and recovery time is required for a joint tap, and few complications tend to occur. The doctor may sometimes administer an injection of pain medicine into the joint after the aspiration is complete, depending on the patient's level of pain.
Most often, the knee is the subject of a joint tap. This procedure may be used when the patient complains of persistent or severe pain. It may also be used if the doctor suspects a joint infection, arthritis, or bursitis, which is inflammation of the bursa, a sac that cushions the joint. In the latter case, joint aspiration can greatly relieve the patient's pain by removing excess fluid that has accumulated around the joint. It may also help increase range-of-motion and relieve pressure on the joint.
Before undergoing a joint tap, patients must inform their doctors of all other medical conditions they have, including allergies, as well as any medications or supplements they take. Occasionally, the patient may be asked to refrain from eating for a period of time prior to the joint aspiration. Sedation may be used if the patient is a child or if he is particularly nervous about the procedure. The area of skin to be injected will be sterilized and a numbing drug is applied to it.
To perform a joint tap, the physician will position the patient in a specific way to allow access to the joint. For example, if the knee is to be aspirated, the patient will lie on a table with the affected knee bent upwards at a 90 degree angle. The doctor will then insert a needle into the joint and draw fluid into a syringe. Patients will have the skin cleaned again and a bandage placed over the area, which should not be removed until the following day.
Minimal recovery time is required for a joint tap. If the knee is aspirated, patients may wish to refrain from walking or standing for long periods at a time. The area will likely be tender for several days.
Patients should discuss the analysis of the joint fluid with their doctors. If the fluid is normal, it should appear clear or light yellow, while cloudy joint fluid may indicate a joint infection or inflammation. The laboratory technician will also examine the sample for uric acid crystals, which indicates gout, as well as other irregularities, such as bacteria and elevated red or white blood cells.
Complications resulting from a joint tap are uncommon and usually mild. Patients should call their doctors if they experience a fever or increasing swelling or pain at the joint. They may need a follow-up appointment if they notice drainage, bleeding, or redness around the site.