What is Knee Arthrocentesis

Knee arthrocentesis is a procedure to remove fluid from the knee joint using a needle. This procedure may be done:

• To relieve pressure in the knee joint.
• To remove excess fluid in the joint before getting an injection of medicine into the knee.
• To get a fluid sample for testing. Testing fluid can help diagnose conditions that can cause fluid buildup in the knee, such as gout, arthritis, rheumatic arthritis, or certain infections.
• To relieve symptoms that are caused by fluid buildup, such as pain, swelling, and stiffness.

Tell a health care provider about:

• Any allergies you have.
• All medicines you are taking, including vitamins, herbs, eye drops, creams, and over-the-counter medicines.
• Any problems you or family members have had with anesthetic medicines.
• Any blood disorders you have.
• Any surgeries you have had.
• Any medical conditions you have, including if you have or think you may have an infection on your skin or any other area of your body.
• Whether you are pregnant or may be pregnant.

What are the risks?

Generally, this is a safe procedure. However, problems may occur, including:

• Infection.
• Bleeding.
• Allergic reaction to medicines.
• Damage to blood vessels, nerves, tendons, or other tissues in the knee joint.
• Swelling, bruising, or soreness.

What happens before the procedure?

• Ask your health care provider about changing or stopping your regular medicines. This is especially important if you are taking diabetes medicines or blood thinners.
• Follow instructions from your health care provider about eating or drinking restrictions.
• Plan to have someone take you home from the hospital or clinic.
• Plan to have a responsible adult care for you for at least 24 hours after you leave the hospital or clinic. This is important.

What happens during the procedure?

• You will sit or lie down.
• Your injection site will be marked with a pen or marker.
• Your knee will be cleaned with a germ-killing (antiseptic) solution.
• You will be given an injection of medicine in the front of your knee, to numb the knee area (local anesthetic).
• If you have a lot of pain or anxiety, you may be given:
  • A medicine to help you relax (sedative).
  • A medicine to make you fall asleep (general anesthetic).
• Your health care provider may use ultrasound to help guide the needle into the correct location in the joint space. Ultrasound creates images of the inside of the body using painless sound waves.
• A long, thin needle will be inserted into the side of your knee joint. You may feel some pressure.
• Your health care provider will pull back the syringe on the needle to remove as much fluid as possible. Your health care provider may press on your knee while doing this to help remove the fluid.
• When your health care provider has removed as much of the fluid as possible, the needle will be removed.
• A bandage (dressing) will be placed over your injection site.

The procedure may vary among health care providers and hospitals.

What happens after the procedure?

• Your blood pressure, heart rate, breathing rate, and blood oxygen level will be monitored until you leave the hospital or clinic.
• Do not drive unless your health care provider approves. You should not drive for 24 hours if you were given a sedative.
• If you had a fluid sample removed for testing, it is up to you to get the results of your procedure. Ask your health care provider, or the department that is doing the procedure, when your results will be ready.

Summary

• Knee arthrocentesis is a procedure to remove fluid from the knee joint using a needle.
• You may experience some soreness at the aspiration site after the procedure.
• Plan to have someone take you home from the hospital or clinic.

Knee Arthrocentesis, Care After

This sheet gives you information about how to care for yourself after your procedure. Your health care provider may also give you more specific instructions. If you have problems or questions, contact your health care provider.

What can I expect after the procedure?

After this procedure, it is common to have:

• Bruising.
• Swelling.
• Soreness.

Follow these instructions at home:

Managing pain, stiffness, and swelling

• If directed, put ice on your knee:
  • Put ice in a plastic bag.
  • Place a towel between your skin and the bag.
  • Leave the ice on for 20 minutes, 2–3 times a day.
• Do not put heat on your knee.
• Wrap your knee to help prevent swelling as told by your health care provider. Ask your health care provider to show you how to wrap your knee.
• Move your toes often to avoid stiffness and to lessen swelling.
• Raise (elevate) your knee above the level of your heart while you are sitting or lying down. To do this, try putting a few pillows under your knee and lower leg.

Bathing

• Do not take baths, swim, or use a hot tub until your health care provider approves. Ask your health care provider if you may take showers.

Activity

• Ask your health care provider what activities are safe for you during recovery, and ask what activities you need to avoid. In some cases, you may be able to return to normal activities right away.

Driving

• Do not drive until your health care provider approves. You should not drive for 24 hours if you were given a medicine to help you relax (sedative) during your procedure.
• Do not drive or use heavy machinery while taking prescription pain medicine.

General instructions

• Take over-the-counter and prescription medicines only as told by your health care provider.
• Check your puncture site every day for signs of infection. Check for:
  • Redness, swelling, or pain.
  • Fluid or blood.
  • Warmth.
  • Pus or a bad smell.
• Change your bandage (dressing) as told by your health care provider. Make sure you wash your hands with soap and water before you change your dressing. If you cannot use soap and water, use hand sanitizer.
• Keep all follow-up visits as told by your health care provider. This is important.

Contact a health care provider if you have:

• Swelling or stiffness that:
  • Gets worse.
  • Becomes severe.
  • Does not get better with medicine.
• A fever.
• Any of the following around your puncture site:
  • Redness, swelling, or pain.
  • Fluid or blood draining.
  • Unusual warmth.
  • Pus or a bad smell.

Get help right away if you have:

• Shortness of breath.
• Severe pain.
• Pain that does not get better with medicine.

Summary

• It is common to have mild soreness for a couple of days after this procedure.
• Talk with your health care provider about how to use ice and wraps to prevent swelling.
• Get help right away if you feel short of breath or have pain that does not get better with medicine.