Arthrocentesis

Removing extra fluid from a joint

What is it?

Joint fluid removal is also called arthrocentesis. A thin needle is inserted into a swollen joint to remove excess fluid. Common joints are the knee, shoulder, elbow, ankle, wrist, and hip. Ultrasound may guide the needle, especially for deeper joints.

A small sample may be sent to the lab. This is a diagnostic aspiration. A larger amount may be removed to ease pressure and pain. This is a therapeutic aspiration. The needle is removed when the procedure is finished. No tube stays in place. Your team may also place medicine, such as a steroid, into the joint after removing the fluid. That is a separate step, done only if it is part of your plan.

Why do I need it?

Extra joint fluid can come from injury, osteoarthritis, inflammatory arthritis, gout, infection, or bleeding into the joint. Swelling can cause:

• Pain, stiffness, and trouble bending or bearing weight
• A tight, swollen joint that limits daily activity
• The need to test fluid for infection, crystals, blood, or inflammation
• Pressure that can be relieved while the cause is treated

How do I prepare?

• Medicines: Tell the team about blood thinners, aspirin, anti-inflammatory drugs, and all other medicines. Do not stop them unless you are told to.
• Allergies: Report allergies to numbing medicine, iodine, latex, or adhesives.
• The joint: Tell the team if you have a joint replacement, a recent injection, or red, broken, or infected skin over the joint.
• Eating and clothing: You can often eat and drink normally. Wear loose clothing that lets the team reach the joint.
• Support: Most people need only local anesthetic. Arrange a ride if sedation is planned.

How is it done?

• You sit or lie so the joint is easy to reach. The skin is cleaned. Ultrasound may be used to find the fluid and avoid nearby structures.
• Local anesthetic numbs the skin. You may feel a brief sting, then pressure. Sharp pain should be reported.
• A needle enters the joint. Fluid is drawn into a syringe. A sample may be sent to the lab.
• The needle is removed, pressure is held, and a bandage is placed. The procedure often takes 10 to 30 minutes.
• You are watched briefly. Many people go home the same day.

Care Instructions

• Keep the bandage on for about 24 hours. You may usually shower after that and pat the site dry. Do not soak the joint in a bath, pool, or hot tub for a few days.
• Rest the joint the day of the procedure. Ice, wrapped in a cloth, for 15 to 20 minutes at a time can ease soreness.
• Avoid heavy lifting, strenuous exercise, and repeated bending of that joint for 24 to 48 hours, or as directed.
• Mild soreness and a small bruise are common. The joint may feel easier to move once the pressure is gone.
• Fluid can return. Follow your team’s plan for activity, medication, or a later injection.

What to watch out for

Call your care team promptly if you notice:

• Increasing redness, warmth, swelling, or drainage of pus at the site
• Fever, chills, or pain that keeps getting worse after the first day
• Numbness, weakness, or new trouble moving the joint
• Bleeding that soaks the bandage, or a joint that becomes much more swollen
• Severe pain, a joint that suddenly will not move, chest pain, trouble breathing, or fainting — seek emergency care