LAB TEST
Knee MRI scan
A knee MRI (magnetic resonance imaging) scan uses energy from strong magnets to create pictures of the knee joint and muscles and tissues. An MRI does not use radiation (x-rays). Single MRI images are called slices. The images can be stored on a computer or printed on film. One exam produces many images.
How the Test is Performed
You will wear a hospital gown or clothes without metal zippers or snaps (such as sweatpants and a t-shirt). Please remove your watches, glasses, jewelry, and wallet. MRI can pull on any metal objects. Certain types of metal can cause blurry images. You will lie on a narrow table that slides into a large tunnel-like…
How to Prepare for the Test
You may be asked not to eat or drink anything for 4 to 6 hours before the scan. Tell your health care provider if you are afraid of closed spaces (have claustrophobia). You may be given a medicine to help you feel sleepy and less anxious. Your provider may suggest an "open" MRI, in which the machine is not as close to…
How the Test will Feel
An MRI exam causes no pain. You will need to lie still. Too much movement can blur MRI images and cause errors. The table may be hard or cold, but you can ask for a blanket or pillow. The machine makes loud thumping and humming noises when turned on. You can wear ear plugs to help block out the noise. An intercom in…
Why the Test is Performed
Your provider may order this test if you have: An abnormal result on a knee x-ray or bone scan A feeling that your knee is giving away in the knee joint Buildup of joint fluid behind the knee ( Baker cyst ) Fluid collecting in the knee joint Infection of the knee joint Knee cap injury Knee pain with fever Knee locking…
Normal Results
A normal result means your knee looks OK.
What Abnormal Results Mean
Abnormal results may be due to a sprain or tear of the ligaments in the knee area. Abnormal results may also be due to: Degeneration or changes that occur with age Meniscus or cartilage injuries Arthritis of the knee Avascular necrosis (also called osteonecrosis) Bone tumor or cancer Broken bone Buildup of joint fluid…
Risks
MRI uses no radiation. There have been no reported side effects from the magnetic fields and radio waves. The most common type of contrast (dye) used is gadolinium. It is very safe. Allergic reactions to the substance are rare. However, gadolinium can be harmful to people with kidney problems that need dialysis. If…
Considerations
Tests that may be done instead of a knee MRI include: CT scan of the knee Knee x-ray
References
Helms CA. Magnetic resonance imaging of the knee. In: Helms CA, ed. Fundamentals of Skeletal Radiology. 5th ed. Philadelphia, PA: Elsevier; 2020:chap 9. Kapoor G, Toms AP. Current status of imaging of the musculoskeletal system. In: Adam A, Dixon AK, Gillard JH, Schaefer-Prokop CM, eds. Grainger & Allison's Diagnostic…
This is a summary. Read the full article at www.ucsfbenioffchildrens.org (reviewed 24/04/2023).
This page is general information and is not medical advice. It does not replace a registered doctor, and it is not a prescription or a recommendation to use any medicine or test. Prices are listed prices and may change. Always follow the advice of your doctor or pharmacist.