A leg MRI (magnetic resonance imaging) scan of the leg uses strong magnets to create pictures of the leg. This may include the ankle, foot, and surrounding tissues.
A leg MRI also creates pictures of the knee.
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.
You will be asked to wear a hospital gown or clothes without metal zippers or snaps (such as sweatpants and a t-shirt). Some types of metal can cause blurry images.
You will lie on a narrow table that slides into a tunnel-like scanner.
Some exams use a special dye (contrast). Most of the time, you will get the dye through a vein in your arm or hand before the test. Sometimes, the dye is given into a joint. The dye helps the radiologist see certain areas more clearly.
During the MRI, the person who operates the machine will watch you from another room. The test most often lasts 30-60 minutes, but may take longer.
You may be asked not to eat or drink anything for 4 - 6 hours before the scan.
Tell your doctor if you are afraid of close spaces (have claustrophobia). You may be given a medicine to help you feel sleepy and less anxious. Your doctor may suggest an "open" MRI, in which the machine is not as close to the body.
Before the test, tell your health care provider if you have:
Because the MRI contains strong magnets, metal objects are not allowed into the room with the MRI scanner:
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 the room allows you to speak to someone at any time. Some MRIs have televisions and special headphones to help the time pass.
There is no recovery time, unless you were given a medicine to relax. After an MRI scan, you can return your normal diet, activity, and medicines.
This test provides detailed pictures of parts of the leg that are hard to see clearly on CT scans.
Your doctor may order an MRI of the leg if you have:
A normal result means your leg looks okay.
Abnormal results may be due to:
Talk to your health care provider about your questions and concerns.
MRI contains 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 are rare. However, gadolinium can be harmful to people with kidney problems that need dialysis. If you have kidney problems, please tell your health care provider before the test.
The strong magnetic fields created during an MRI can cause heart pacemakers and other implants to not work as well. It can also cause a piece of metal inside your body to move or shift. For safety reasons, please don't bring anything that contains metal into the scanner room.
Tests that may be done instead of an MRI include:
A CT scan may be preferred in an emergency. The test is faster than MRI and often available in the emergency room.
MRI - lower extremity; Magnetic resonance imaging - leg; Magnetic resonance imaging - lower extremity; MRI - ankle; Magnetic resonance imaging - ankle; MRI - femur; MRI - leg
Wilkinson ID, Paley MNJ. Magnetic resonance imaging: basic principles. In: Grainger RC, Allison D, Adam, Dixon AK, eds. Diagnostic Radiology: A Textbook of Medical Imaging. 5th ed. New York, NY: Churchill Livingstone; 2008:chap 5.
DeLee JC, Drez D Jr, Miller MD, eds. DeLee and Drez’s Orthopaedic Sports Medicine. 3rd ed. Philadelphia, Pa: Saunders Elsevier; 2009:chap 24.
Grainger RG, Thomsen HS, Morcos SK, Koh DM, Roditi G. Intravascular contrast media for radiology, CT, and MRI. In: Adam A, Dixon AK, eds. Grainger & Allison's Diagnostic Radiology: A Textbook of Medical Imaging. 5th ed. New York, NY: Churchill Livingstone; 2008:chap 2.
Updated by: C. Benjamin Ma, MD, Assistant Professor, Chief, Sports Medicine and Shoulder Service, UCSF Department of Orthopaedic Surgery. Also reviewed by A.D.A.M. Health Solutions, Ebix, Inc., Editorial Team: David Zieve, MD, MHA, Bethanne Black, Stephanie Slon, and Nissi Wang.
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