Magnetic Resonance Imaging (MRI) of the Knee
Magnetic resonance imaging (MRI) is a test
done with a large machine that uses a magnetic field and pulses of radio wave
energy to make pictures of the knee . Muscles,
cartilage, and other joint structures are often best
seen with an MRI. In many cases MRI gives information about structures in the
body that cannot be seen as well with an
For an MRI test, you are placed
inside the magnet so that your knee is inside the strong magnetic field. MRI
can find changes in the structure of organs or other tissues. It also can find
tissue damage or disease, such as infection or a tumor. Pictures from an MRI
scan are digital images that can be saved and stored on a computer for further
study. The images also can be reviewed remotely, such as in a clinic or an
operating room. Photographs or films of selected pictures can also be made.
In some cases, a
contrast material may be used during the MRI scan to
show certain structures more clearly in the pictures. The contrast material may
be used to check blood flow, find some types of tumors, and show areas of
inflammation or infection. The contrast material may be put in a vein (IV) in your arm or directly into your knee.
There are two main types of MRI—the standard MRI machine and the
open MRI machine .
Why It Is Done
Magnetic resonance imaging (MRI) of the
knee is done to:
- Check for the cause of unexplained knee pain or
the knee giving out for no reason.
- Find problems in the knee joint ,
arthritis, bone tumors, or infection, or damaged
meniscus , ligaments, or
- Find out if a knee
arthroscopy is needed.
MRI may also find a bone fracture when X-rays and other
tests do not give a clear answer. MRI is done more commonly than other tests to
check for certain bone and joint problems.
How To Prepare
Before your MRI test, tell your doctor
and the MRI technologist if you:
- Are allergic to any medicines. The contrast
material used for MRI does not contain iodine. If you know that you are allergic to the contrast material used for the MRI, tell your doctor before having another test.
- Are or might be pregnant.
- Have metal screws in
your knee from a past knee surgery.
- Have any metal implanted in your body. This helps your doctor know if the test is safe for you. Tell your doctor if you have:
- Heart and blood vessel devices such as a coronary artery stent, pacemaker, ICD (implantable cardioverter-defibrillator), or metal heart valve.
- Metal pins, clips, or metal parts in your body, including artificial limbs and dental work or braces.
- Any other implanted medical device, such as a medicine infusion pump or a cochlear implant.
- Cosmetic metal implants, such as in your ears, or tattooed eyeliner.
- Had recent surgery on a blood vessel. In some cases, you may
not be able to have the MRI test.
- Have an intrauterine device (IUD) in place. An IUD may prevent
you from having the MRI test done.
- Become very nervous in confined
spaces. You need to lie very still inside the MRI magnet, so you may need
medicine to help you relax. Or you may be able to have the test done with open
MRI equipment. It is not as confining as standard MRI machines. You may need
medicine to help you relax.
- Have any other health conditions, such as kidney problems or
sickle cell anemia, that may prevent you from having
an MRI using contrast material.
- Wear any medicine patches. The MRI may cause a burn at the patch