Is a Knee CT Scan?
A computed tomography (CT) scan is a type of X-ray that shows
cross-sectional images of a specific area on your body. For example, a CT scan
of your knee would help doctors diagnose disease or inspect injuries on your
A CT scanner circles the body and sends images to a computer. The
computer uses these images to make detailed pictures. This allows doctors and
trained technicians to see the muscles, tendons, ligaments, vessels, and bones
that make up your knee.
A CT scan is also sometimes referred to as a CAT scan. The scan
is performed at a hospital or specialized outpatient testing facility.
Is a Knee CT Scan Done?
A CT scan provides your doctor with more detailed images of the
inside of your knee than traditional X-rays do. It gives your doctor an
internal view of your knee without making an incision and performing
exploratory surgery. This can help your doctor provide a more accurate
diagnosis for knee problems, which can include:
- collection of pus (abscess)
- fractured bone
- torn ligaments or tendons
Risks of a Knee CT Scan
There are very few risks associated with a CT scan. Occasionally,
the dye used in the procedure can cause temporary damage to your kidneys. This
risk is greater if your kidneys have already been affected by disease or
infection. There are newer dyes that carry much less risk to the kidneys.
As with any X-ray, there is some exposure to radiation. The level
is so low that it’s usually harmless. If you’re pregnant or could be pregnant,
speak with your doctor. Any potential exposure to radiation could be harmful to
a developing fetus.
to Prepare for a Knee CT Scan
Before your exam, your doctor will provide you with complete
instructions on how to prepare for your knee CT scan.
In some cases, your doctor may use contrast dye. Contrast dye helps
provide better images by reacting with the imaging equipment. If you’ve had an
allergic reaction to similar dyes in the past, tell your doctor before the
test. The most common dye used contains iodine, so tell your doctor if you’re
allergic to iodine.
If you’re receiving dye, your doctor may instruct you to avoid
foods and liquids for four to six hours before the CT scan.
You’ll also have to remove all your jewelry and change into a
hospital gown before the surgery. You’ll need to remove any braces or bandaging
worn over your affected knee.
a Knee CT Scan Is Performed
If your doctor is using contrast dye for the scan, you’ll be
given the dye intravenously. This means that a nurse will inject the contrast
dye into one of your veins. You’ll typically need to wait an hour for the dye
to work its way through your body before the scan can begin.
The CT machine looks like a large doughnut made of metal and
plastic that is standing on its side. It has a sliding, moveable bench in its
center. During the scan, you’ll lie on the bench. The technician will move the
bench in and out of the machine using a remote control.
The technician may require you to lie in a specific position
during the test. They may use pillows or straps to ensure you stay in the correct
position long enough to get a quality image. You may also have to hold your
breath briefly during specific scans. Talk to your doctor beforehand if you
think you’ll have trouble staying still.
After a round of scans, you may be required to wait for a short
time while the technician reviews the images to ensure they are clear enough
for your doctor to read them correctly.
A typical CT scan of the knee takes between 30 and 45 minutes to
Up After the Knee CT Scan
After the test, you’ll be able to go about your day normally.
If you’ve received contrast dye, you may want to drink extra
fluids to help flush the dye out of your system. All traces of the dye are
typically gone within 24 hours.
Results for a knee CT scan usually take a day to process. Your
doctor will schedule a follow-up appointment to discuss the results. Together
you’ll be able to decide how to proceed based on the evaluation of your scans.