Arthrocentesis is a common medical procedure involving a joint, often performed to address swelling or discomfort. It involves using a needle and syringe to interact with the fluid inside a joint. This procedure can both help diagnose the cause of joint issues and provide relief from symptoms.
Understanding Arthrocentesis
Arthrocentesis, also known as joint aspiration, involves withdrawing fluid, called synovial fluid, from a joint. This procedure serves two main purposes: diagnostic and therapeutic. For diagnostic purposes, the collected fluid can be analyzed in a laboratory to identify the cause of joint pain, inflammation, or swelling. This analysis can help detect infections like septic arthritis, or conditions such as gout or pseudogout, by examining factors like white blood cell count, presence of crystals, or bacterial cultures.
The therapeutic use of arthrocentesis focuses on relieving discomfort by removing excess fluid that causes pressure and pain within the joint. After fluid removal, medication like corticosteroids or hyaluronic acid may be injected into the joint space to reduce inflammation or improve lubrication. This procedure is commonly performed on large, easily accessible joints such as the knee, shoulder, hip, and ankle.
The Procedure Steps
Arthrocentesis is an outpatient procedure, often completed in 5 to 10 minutes. The patient is positioned comfortably, either sitting or lying down, to allow easy access to the affected joint.
Before needle insertion, the healthcare provider marks the precise entry point on the skin. The area around the joint is then thoroughly cleaned with an antiseptic solution, such as povidone-iodine or chlorhexidine, to minimize the risk of infection. A local anesthetic, often 1% lidocaine, is then administered to numb the skin and deeper tissues along the needle’s path, which helps reduce discomfort during the procedure.
Once the area is numb, a sterile needle, typically 18- or 20-gauge, attached to a syringe, is carefully inserted into the joint space. In some cases, medical imaging like ultrasound or fluoroscopy guides the needle to ensure accurate placement, particularly for deeper joints like the hip. As the needle enters the joint capsule, the practitioner gently pulls back on the syringe plunger to aspirate the synovial fluid. Fluid is removed, using additional syringes if needed.
If a therapeutic injection is also planned, the same needle may remain in place while the fluid-filled syringe is replaced with one containing medication. After the procedure, the needle is withdrawn, and a small bandage is applied to the site.
Preparing for and Recovering from Arthrocentesis
Before undergoing arthrocentesis, patients should provide their doctor with a complete medical history, including all current medications and any known allergies. It is important to inform the doctor about any blood thinners or anticoagulants, as adjustments to these medications might be necessary before the procedure. Fasting is not required unless general anesthesia or specific fluid tests are planned.
Following the procedure, patients can return home the same day. Mild soreness, tenderness, and bruising at the injection site are common for a day or two. Applying ice packs to the affected joint and elevating the limb can help reduce swelling and discomfort. Some patients may be advised to rest the joint for 4 to 24 hours and may need someone to drive them home, especially if a sedative was administered.
Over-the-counter pain relievers may be recommended, though patients should confirm with their doctor. Patients should contact their healthcare provider immediately if they experience worsening pain not relieved by medication, fever, chills, excessive redness, warmth, or discharge from the injection site.
Potential Risks
While arthrocentesis is a safe procedure, potential risks and complications exist. Minor and temporary side effects include localized pain, swelling, and bruising at the needle insertion site. Skin discoloration from bleeding under the surface is also possible.
More serious, but rare, complications can occur. Infection, known as septic arthritis, is a concern if sterile techniques are not strictly followed. Other rare risks include bleeding into the joint (hemarthrosis) and nerve damage. Allergic reactions to the local anesthetic or injected medications are also possible.