About a CT scan of the Achilles tendon
The Achilles tendon is the large tendon at the back of the ankle, connecting the calf muscles to the heel bone (calcaneus). It is the strongest tendon in the body and is used every time you walk, run or jump. A CT (computed tomography) scan uses X-rays and a computer to make detailed cross-section pictures, and is especially good at showing bone and calcium.
For most problems with the tendon itself, such as Achilles tendinopathy (pain and stiffness from wear) or a tear or rupture, ultrasound or MRI is the better test, as they show soft tissue in much more detail. You can read about this on our Achilles tendon MRI page. A CT may be used when the question is about bone or calcium, for example:
- calcium deposits in the tendon (calcific tendinopathy), showing their exact size and position before surgery
- a bony bump on the back of the heel (Haglund’s deformity) or bone spurs where the tendon attaches
- a piece of bone pulled off the heel with the tendon (an avulsion fracture)
- when MRI is not possible, for example if you have a pacemaker or other device that is not safe for MRI
Your referrer will say which scan is best. When you book, choose the left or right side.
What happens during the scan
You lie on the scanner bed, usually feet first, with your foot and ankle supported by pads so they stay still. Only your lower leg goes through the scanner, which is a short, open ring. The radiographer controls the scanner from the next room, but can see, hear and talk to you throughout. The scan itself takes only a few minutes. Contrast dye is not usually needed; where contrast is needed, it is charged separately.
Is CT safe?
CT uses X-rays, which are a type of ionising radiation. A CT of the ankle and heel gives a low dose, because the area scanned is small and far from the organs most sensitive to radiation. The risk from a single scan is very small, and every CT scan is checked by a radiologist or radiographer to make sure the benefit of the scan outweighs the risk, as required by the Ionising Radiation (Medical Exposure) Regulations. If you have had other CT scans recently, tell us when you book.
What the scan can show
A CT scan of the Achilles tendon area can help to look at:
- calcium deposits in the tendon
- Haglund’s deformity and bone spurs on the heel
- avulsion fractures of the heel bone
- other fractures and bone changes around the heel
- planning for surgery
When to get urgent help: go to A&E or an urgent treatment centre if you feel a sudden snap or pop at the back of your ankle, followed by pain and difficulty walking or standing on tiptoe. This may be a ruptured Achilles tendon, which is best treated early.
Preparing for your scan
No special preparation is needed, and you can eat and drink normally. Wear clothing that lets you easily uncover your lower leg. Upload any previous X-ray, ultrasound or MRI reports when you book, and remember to choose the correct side.
Wear loose, comfortable clothing without metal zips, poppers or buttons, and leave jewellery at home, as metal in the scan area can affect the pictures. You may be asked to change into a gown. Unlike MRI, CT is not affected by pacemakers or most metal implants, and the scanner is a short open ring rather than a tunnel, so it is usually easier for people who feel anxious in enclosed spaces.
Tell the team before your scan if you are, or might be, pregnant or breastfeeding, if you have kidney problems, diabetes (especially if you take metformin), asthma, thyroid problems or allergies, or if you have had a reaction to contrast dye before. If you need contrast, you may be asked for a recent kidney blood test result.
Frequently asked questions
Is CT or MRI better for the Achilles tendon?
MRI and ultrasound are usually better for the tendon itself, including tears and tendinopathy. CT is better for the bone and calcium deposits, and is often used to plan surgery. Your referrer will say which is needed; if you are unsure, contact us before booking.
Can CT show an Achilles tendon rupture?
A CT can sometimes show a rupture, but ultrasound or MRI is normally used, as they show the tendon more clearly and do not use radiation. A rupture is usually diagnosed by examination.
Do I need to choose a side?
Yes. Choose the left or right side when you book. If both sides need scanning, contact us so the centre can plan the appointment.
Do I need a referral?
Because CT uses radiation, each scan has to be justified by a qualified professional before it can go ahead. Upload a referral from your GP or consultant when you book if you have one. If you do not, select “no referral” and the scanning centre will review your request and confirm the next steps with you, which may include arranging a referral.
Sources
- MRI of the Achilles tendon – A comprehensive pictorial review. Part one (PMC)
- Terminology for Achilles tendon related disorders (PMC)
- NHS – Heel pain
- NHS – CT scan
- UKHSA – Patient dose information: guidance
The information on this page has been gathered from various sources and is provided for general information only. It is not medical advice. TOP MRI is not liable for the accuracy or completeness of this information. Please speak to your doctor or the scanning centre about your own situation.