MRI Guide: Foot and Ankle

Each foot is comprised of 26 bones and 30 joints. Not to mention the additional muscles, tendons and ligaments. With so many structures and important junctures, if you are experiencing foot pain or ankle pain it can be difficult to pinpoint. Foot and ankle pain is typically described as a dull ache that increases in severity when weight-bearing.

The pain can sometimes feel insignificant, and we brush it off as a mild ankle roll or minor strain. The majority of foot pain is associated with sprains and strains–which require ice, elevation and keeping off the affected foot. If your pain has not improved with these remedies, it can be a sign of a more serious issue.

If you are experiencing this type of recurring or worsening foot or ankle pain, it is important to contact your doctor. They may order a foot and ankle MRI scan to help identify the root cause of your discomfort. Follow along as we will discuss the process of a foot MRI, how to read the resulting images of an MRI scan, and what to expect from the procedure.

What is a Foot and Ankle MRI?

Foot and ankle injuries are common in those who play sports or have a physically demanding job, and are also common after tripping or rolling over on the ankle. A foot and ankle MRI is a type of medical imaging scan that focuses on the foot and ankle area to assess for damage and to discover the cause of pain in the foot and ankle joint.

What Do You See In a Foot MRI?

A magnetic resonance imaging (MRI) scan uses radio waves and a powerful magnetic field to generate images of a specified area of the body. During a foot and ankle MRI procedure, pictures–also referred to as slices–of the ankle and foot will be produced.

These images will show various structures of the area, including:

• Bones
  • Bottom of Tibia and Fibula
  • Talus
  • Calcaneus
  • Tarsals
  • Metatarsals
  • Phalanges
  • Sesamoids
• Muscles
  • Peroneals
  • Gastrocnemius
  • Soleus
  • Tibialis Posterior
  • Tibialis Anterior
  • Tibialis Peroneal
  • Extensors
  • Flexors
• Ligaments & Tendons
  • Achilles tendon
  • Lateral ligament complex
  • Plantar fascia
  • Plantar calcaneonavicular ligament
  • Calcaneocuboid ligament
• Additional Surrounding Soft Tissues

A radiologist will use the resulting images to identify any abnormalities. Such as tendon tears, inflammation, cartilage deterioration, or tumours.

Reasons for a Foot and Ankle MRI

Pain, swelling and instability in the foot and ankle are the most common reasons for having a foot and ankle MRI scan. This could be following an accident where you twisted your ankle joint or a heavy object fell onto your foot, or it could be due to pain and mobility problems with no obvious cause. 

A foot and ankle MRI can diagnose a range of conditions, including:

• Ankle sprains

• Broken bones 

• Bone abnormalities

• Plantar fasciitis (inflammation of the plantar aponeurosis, a thick band of tissue in the sole that provides support and stability) 

• Swelling in the bones (bone marrow oedema) 

• Stress fractures

• Repetitive microtrauma to the bones or soft tissues caused by repetitive stress movements 

• A complete, or full-thickness tear to a ligament or tendon, most commonly in one or both of the peroneal tendons (the peroneal brevis tendon and peroneal longus tendon) that stabilise the foot and ankle 

• Tarsal tunnel syndrome (damage to the nerve in the ankle that runs through the distal tibia and distal fibula, the ends of the tibia and fibula leg bones that join the foot via the ankle) 

• Flat foot deformity 

• Cartilage injuries 

What Can Be Diagnosed By a Foot & Ankle MRI?

With almost a quarter of the body’s bones located in the feet, there are numerous potential causes of injury. Although physical examinations are important, with so many structures in a confined area, an MRI scan can provide more detailed information. This allows doctors the opportunity to diagnose potentially serious issues.

These include:

• Arthritis
• Fracture
• Tendon Tears
• Gout
• Lesions or Tumours
• Inflammation
• Infection

By increasing the accuracy of a diagnosis, an MRI can help find the correct treatment plan needed to alleviate your pain.

How a Foot and Ankle MRI Works

An MRI scanner uses radio waves and strong magnetic fields to create detailed images of the inside of the body. Each tissue in the foot and ankle, from the metatarsal bones (the long bones of the front of the foot) and the navicular bone (one of the small ankle bones) to the soft tissues including the deltoid ligament that supports the side of the foot, and the anterior talofibular ligament and posterior talofibular ligament that provide stability to the front and back of the ankle, contain hydrogen atoms. 

During an MRI, the radio waves and magnets temporarily disrupt these hydrogen atoms, causing them to scatter and then realign. As they do, they create energy, each different tissue type creating different energy. Powerful computers detect these different energies, and turn them into distinct images. A radiologist can interpret these images and use them to detect differences between, for example, a normal achilles tendon and a ruptured one, or a fine fracture line to one of the foot bones. 

How to Read An MRI of The Foot?

To understand how to read an MRI we must first discuss how MRI images are generated. An MRI takes slices across three planes:

• Axial - Top Down
• Coronal - Front to back
• Sagittal - Side to side

Each image shows the structures of the ankle and foot as the MRI moves across each plane.

When a radiologist or radiographer interprets the results of an MRI, they are primarily looking for discolouration. The bones of the scan will appear to be dark grey. If there are patches of lighter or darker colours, it could indicate fluid collection, fracture, or abnormal growth.

Similar to the bones, the muscles and ligaments will also be different colours, usually light grey. The cartilage between the bones will appear very light, almost white. If there is discolouration in these structures it can indicate a tear, deterioration, or infection.

Radiologists are specially trained in identifying even the small nuances of MRI images.

Can An MRI Fix Foot & Ankle Pain?

MRI scans are powerful diagnostic tools. They cannot fix pain during the procedure. However, they do possess the ability to identify the potential cause of your foot or ankle pain.

By identifying the culprit of your discomfort, a treatment plan can be prescribed to begin your recovery and alleviate your pain.

How Long Does A Foot & Ankle MRI Take?

The average foot and ankle MRI scan takes approximately 10–30 minutes. The scan requires you to remain extremely still. Small movements can cause distorted images and result in a longer scan.

How Is a Foot MRI Performed?

On the day of your MRI scan, you can expect:

1. Change Clothing - You will be brought to a room where you will change into a hospital gown. Some clinics allow you to wear your loose-fitting clothing, each will have its policies. All metal must be removed, including jewellery and piercings. Metal can interfere with the results of the scan, causing blurred or distorted images.
2. Brought to Exam Room - You will be instructed to lay down on the MRI table, feet first. Your head will not enter the machine. The radiographer may use foam pillows or another brace to keep your foot and ankle in the correct position for the scan.
3. Contrast IV - Some types of scans require an IV of contrast material. This is used to highlight certain structures more clearly in the scan. If needed you will have an IV administered, it will take a few minutes for the contrast material to make its way around your body. You may feel a temperature change, this is a common response and is to be expected.
4. Scan Begins - The table will slide into the MRI machine. The machine will make loud banging noises during the scan. This is perfectly normal and should not be cause for alarm. Focus on remaining as still as possible to ensure an accurate result. If you are uncomfortable at any point, simply inform the technician and they will work to make you as comfortable as possible. If you are claustrophobic you can ask for a mild sedative beforehand to help keep calm during the procedure.
5. Contrast IV Removal - Once the scan has completed, if an IV was administered, it will be removed. Take your time sitting up and standing, you may feel a little dizzy from contrast material and from laying down for a long period.
6. Change and Leave - You will be brought back to the original room where you can change back into your clothing and gather your belongings. If you have taken a sedative, you cannot operate a vehicle for several hours. Otherwise, you are free to continue your day.
7. Wait for Results - The radiologist will look over the images from your scan. Typically they will forward these to your doctor, along with their diagnosis. Your doctor will then contact you to discuss the results and prescribe a treatment plan–if needed.

Benefits

MRI scans are generally suitable for everyone, and they’re quick, painless and effective at diagnosing the causes of heel pain, ankle instability and ligament injuries. Unlike x-rays and CT scans, MRI scans don’t use radiation to produce detailed images of the inside of the body, so there’s no risk of radiation exposure. 

Risks and Side Effects

Some foot and ankle MRI scans require the use of a contrast dye to highlight certain areas, such as blood flow to the soft tissues, including the medial ligaments that wrap around the inside of the ankle and provide stability. These dyes generally contain iodine or gadolinium, which some people are allergic to. Symptoms of an allergy include feeling breathless, weak and sweaty. If you begin to feel unwell, let your radiologist know straight away. 

The closed nature of an MRI scanner can also make some people feel claustrophobic or panicked. Your medical team can provide a mild sedative if you think you may struggle. 

How to Prepare for a Foot and Ankle MRI

An MRI of the foot and ankle requires little preparation. Unless otherwise advised, you can eat and drink as normal before your scan, and take any regular medications. 

Getting the Results

You will normally need to wait a few days for your results, once your radiologist has taken a look and discussed them with your referring doctor who can then refer you to a physical therapy specialist or recommend the right pain relief or surgery. 

Costs

In the UK, a private foot and ankle MRI scan costs between £200 and £500, depending on the clinic and your medical history.

The Bottom Line

It can be difficult to determine what threshold of pain is enough to have ankle or foot pain examined. If you have lasting or worsening foot pain, it is important to contact your doctor as soon as possible. What might seem like a small strain could be a more serious problem.

An MRI scan is a tool to help you get back to living without foot and ankle pain. At Scan.com we are committed to your health and wellness. If you are interested in avoiding the long wait times at the NHS, book an appointment with one of our centres in as little as 5 working days. Or if you would like additional information, contact us, our team is here to answer any questions you may have.

References

1. https://www.arthritis.org/health-wellness/about-arthritis/where-it-hurts/anatomy-of-the-foot
2. https://www.foothealthfacts.org/conditions/ankle-pain
3. https://two-views.com/mri-imaging/foot-scan.html
4. https://www.elliothospital.org/website/diagnostic-imaging-mri-foot.php
5. https://radiologyassistant.nl/musculoskeletal/ankle/mri-examination
6. https://orthopaedia.com/page/Anatomy-of-the-Foot-Ankle
7. https://www.coloradospineinstitute.com/education/tests/mri/