Arthrocentesis, also known as joint aspiration, is a medical procedure that involves removing fluid from a joint using a hollow needle. The term combines “arthro,” meaning joint, and “centesis,” referring to a surgical puncture to draw fluid. This technique helps identify the cause of joint issues and provides direct relief from symptoms.
Understanding the Purpose
Arthrocentesis serves distinct diagnostic and therapeutic purposes in managing joint conditions. Diagnostically, the procedure allows for the collection of synovial fluid, the natural lubricant found within joints, for laboratory analysis. This analysis helps identify underlying issues such as infection, inflammation, or the presence of crystals that point to conditions like gout or pseudogout. Fluid analysis, including appearance, cell count, and chemical composition, provides insights into joint health.
Therapeutically, arthrocentesis aims to alleviate discomfort and improve joint function. Removing excess fluid from a swollen joint can immediately reduce pressure and pain, as well as enhance range of motion. This aspiration can also create space for the injection of medications directly into the joint. Commonly, corticosteroids are administered to reduce inflammation and pain. Hyaluronic acid injections may also lubricate the joint and improve cushioning, particularly for osteoarthritis.
The Procedure Explained
The procedure begins with patient positioning to ensure the affected joint is accessible and comfortable. For a knee aspiration, the patient might lie down with the leg slightly bent or extended. The healthcare provider then thoroughly cleans the skin around the injection site with an antiseptic solution to minimize the risk of infection.
A local anesthetic is typically applied or injected to numb the skin and deeper tissues, ensuring comfort during needle insertion. For deeper or smaller joints, imaging guidance like ultrasound may be used to precisely locate the joint space and guide the needle. Once the area is numb, a sterile needle, often an 18- or 20-gauge, is carefully inserted into the joint capsule.
As the needle enters the joint, the healthcare provider gently pulls back on the attached syringe to aspirate the synovial fluid. As much excess fluid as possible is removed to relieve pressure. If medication is to be injected, the same needle may remain in place while the fluid-filled syringe is replaced with one containing the medication. After fluid aspiration or medication injection, the needle is withdrawn and a small bandage is applied. The entire process typically takes about 10 to 15 minutes.
What to Expect Afterward
Following arthrocentesis, mild soreness, discomfort, or bruising at the injection site is common. This sensation usually subsides within hours to a couple of days. Applying ice and resting the affected area can help manage discomfort and swelling.
Patients are generally advised to avoid strenuous activities for 4 to 24 hours to allow for proper healing. Depending on the reason for the procedure, relief from pain and swelling may begin within a day or so. If diagnostic fluid analysis was performed, results are typically sent to the referring doctor and may take time to process, depending on the tests ordered. Your healthcare provider will discuss these results and any further treatment plans during a follow-up.
Potential Risks
While generally safe, arthrocentesis carries a few potential risks. Common minor side effects include temporary pain, swelling, and bruising at the needle insertion site. Some individuals might also experience localized warmth around the joint.
More serious complications are rare but can include infection from bacteria introduced into the joint space. Bleeding into the joint (hemarthrosis) is also a rare possibility, especially for those with bleeding disorders. Allergic reactions to the anesthetic or injected medications are uncommon. Damage to surrounding structures like cartilage, tendons, nerves, or blood vessels is also rare, though healthcare providers take precautions.