Another name for a joint aspiration is arthrocentesis. This simple procedure is a tool used for diagnosing a patient’s condition. A needle is inserted into a joint for the purpose of drawing out fluid, called synovial fluid. The fluid is then sent to a laboratory for analysis.
A doctor may recommend a joint aspiration if the patient has unexplained pain in the joint. Other possible symptoms that may warrant this procedure are joint inflammation, redness, and swelling. A joint aspiration may help a doctor diagnose conditions such as an infection or arthritis. Sometimes, the very act of withdrawing fluid may help to relieve the patient’s pain and swelling. It may do this by reducing the pressure of excess accumulated fluid within the joint.
In preparation for a joint aspiration, the doctor will typically ask for the patient’s medical history. The patient should disclose any allergies and medical conditions. Additionally, the doctor should know if the patient has recently taken antibiotics, as these drugs may affect the results of the lab test.
Before inserting the needle, the doctor will typically apply a topical cream to the joint to numb the area. For very young patients, the doctor may also administer a sedative to render the patient unconscious. If a sedative is administered, the patient will be unable to eat or drink for a while before the procedure, in order to avoid vomiting.
Following the application of topical cream or a sedative, the doctor will position the patient on the exam table to allow him access to the joint. The area will be disinfected. If the patient is conscious, an additional anesthetic drug may be injected into the area. For unconscious patients, the doctor will continually monitor the vital signs, such as blood pressure and heart rate, in case of any complications.
A needle is then inserted into the joint. Occasionally, a doctor may also use an x-ray to ensure the accurate positioning of the needle. Synovial fluid is then collected in a syringe. The doctor will apply a bandage to the area after the procedure to help prevent infection.
When the fluid is sent to the lab, a technician will analyze the sample by placing it in a laboratory dish. He will then observe the sample to see if any microorganisms — such as viruses, bacteria, or fungi — grow in the sample. He may also run tests to determine protein levels, blood cell count, and glucose levels. The doctor will then analyze any abnormalities that the lab has detected in the sample, to provide the patient with a diagnosis.
There are few risks associated with a joint aspiration. Occasionally, the patient may contract an infection in the area. Bleeding may also occur. In general, a joint aspiration is a safe, diagnostic procedure.