How to Understand Ankle MRI Terms: A Patient's Guide
Updated: 4 days ago
An ankle MRI report can be full of unfamiliar words, like "ATFL," "bone marrow edema," and "osteochondral lesion." This guide explains the most common ankle MRI terms in plain language, so you can follow your report and ask your doctor better questions. Your doctor is the best person to explain what your own results mean.
What is in an ankle MRI report?
An MRI uses a strong magnet and radio waves, not X-rays, to make detailed pictures of the ankle. It shows bones, ligaments, tendons, cartilage, and fluid. A radiologist, a doctor trained to read medical images, reviews the pictures and writes a report for your doctor.
Most reports include:
Exam: the body part and scan type, such as "MRI right ankle without contrast"
History or indication: why the scan was ordered, such as pain after a sprain
Findings: what the radiologist saw in the bones, ligaments, tendons, and joint
Impression: a short summary of the most important findings
Start with the impression, then use the findings and this guide for the details. For a general overview, see how to read your radiology report.
Ankle anatomy terms
Tibia: The large shinbone. Its lower end forms the inner bump of the ankle, called the medial malleolus.
Fibula: The thinner bone on the outer side of the leg. Its lower end forms the outer ankle bump, called the lateral malleolus.
Talus: The bone that sits between the tibia and fibula and the heel bone. It forms the main ankle joint.
Calcaneus: The heel bone.
Ankle joint (tibiotalar joint): The joint where the tibia and fibula meet the talus. It mainly lets the foot point up (dorsiflexion) and down (plantarflexion).
Subtalar joint: The joint just below the ankle, between the talus and calcaneus. It helps the foot tilt in and out (inversion and eversion), which helps you walk on uneven ground.
Articular cartilage: The smooth layer covering the ends of the bones inside a joint.
Ligament terms
Ligaments are strong bands that connect bone to bone. Ankle reports often name them with abbreviations.
ATFL (anterior talofibular ligament): A ligament on the outer front of the ankle. It is the ligament most often hurt in a common ankle sprain.
CFL (calcaneofibular ligament): A ligament on the outer side that connects the fibula to the heel bone. It is often hurt along with the ATFL in more serious sprains.
PTFL (posterior talofibular ligament): A ligament on the outer back of the ankle. It is injured less often.
Deltoid ligament: A group of strong ligaments on the inner side of the ankle.
Syndesmosis: The ligaments that hold the lower tibia and fibula together just above the ankle joint. An injury here is often called a "high ankle sprain."
How ligament injuries are described
Reports use words that describe how much of the ligament looks damaged:
Grade | Common meaning | What the report may say |
Grade 1 | Mild sprain, the ligament is stretched | Swelling or fluid around the ligament, fibers look intact |
Grade 2 | Partial tear | Some fibers are torn, with swelling |
Grade 3 | Complete tear | The ligament is torn all the way through |
You may also see words like "thickened," "attenuated" (thinned), or "chronic." These can point to an older injury that has healed in a stretched or scarred way. Grading systems can vary, so ask your doctor what the words mean in your report.
Tendon terms
Tendons connect muscles to bones. Radiologists often look at ankle tendons by area:
Back: the Achilles tendon, which connects the calf muscles to the heel
Outer side: the peroneal tendons (peroneus longus and peroneus brevis), which run behind the outer ankle bump
Inner side: the posterior tibialis tendon, plus the flexor tendons of the toes
Front: the extensor tendons, including the anterior tibialis tendon
Common tendon words include:
Tendinosis or tendinopathy: Wear-and-tear changes in a tendon. The tendon may look thick or have a changed signal.
Tenosynovitis: Irritation of the thin sheath around a tendon, often with fluid around it.
Split tear: A lengthwise tear in a tendon. This term is often used for the peroneus brevis tendon.
Partial or complete tear (rupture): A tear that goes part of the way or all the way through the tendon.
Subluxation or dislocation: The tendon slips partly or fully out of its normal groove. This can happen with the peroneal tendons.
Bone and cartilage terms
Bone marrow edema: Extra fluid inside the bone. It can show up after an injury, with stress on the bone, or with arthritis. It is a finding, not a diagnosis by itself. It can also be called a "bone bruise" when it follows an injury.
Stress fracture or stress reaction: A small crack or early stress injury in a bone, often from repeated activity. MRI can show stress injuries that may not show up on an X-ray.
Fracture: A break in the bone. MRI may show a fracture line and swelling around it.
Osteochondral lesion (OCL): An injury to the cartilage and the bone just under it. In the ankle, this often affects the top of the talus. The report may describe its size, whether the cartilage is intact, and whether a piece looks loose.
Osteochondritis dissecans (OCD): A condition where a piece of bone and cartilage separates, or starts to separate, from the surrounding bone. Radiologists may describe whether the piece looks stable or unstable.
Loose body: A small piece of bone or cartilage floating in the joint.
Joint and soft tissue terms
Joint effusion: More fluid than normal in the joint. A small amount of fluid is normal. More fluid can come with injury or irritation.
Synovitis: Irritation of the joint lining (synovium). It may show up as a thickened lining or extra fluid.
Sinus tarsi: A small space on the outer side of the foot between the talus and calcaneus. The report may describe fluid or scarring here.
Plantar fascia: A thick band of tissue along the bottom of the foot. An ankle MRI may include it if heel pain is a concern.
Small extra bones and impingement
Accessory ossicle: A small extra bone that some people are born with. Many cause no problems.
Os trigonum: A small extra bone at the back of the ankle. In some people, especially those who point the foot often, such as dancers, it can be linked to pain at the back of the ankle. This is called posterior impingement.
Accessory muscle: An extra muscle that some people have near the ankle. It is usually harmless but is sometimes noted in the report.
Impingement: Pinching of soft tissue or bone when the ankle moves. It can happen in the front or the back of the ankle. Impingement is diagnosed mainly by your doctor's exam, with the MRI as support.
Words that sound scary but may be common
Some findings show up often and may not explain your pain, such as small amounts of joint fluid, an extra bone, or signs of an old sprain. A finding does not always explain your symptoms. That is why your doctor looks at the MRI together with your exam and history. If your report says "clinical correlation recommended," it simply means the radiologist wants your doctor to compare the images with your symptoms. Our guide to decoding the language of MRI reports explains more phrases like this.
If you are still deciding whether imaging makes sense after an injury, read do I need an MRI for a sprained ankle.
Frequently asked questions
What does ATFL tear mean on an ankle MRI?
It means the anterior talofibular ligament, on the outer front of the ankle, is torn. The report may say whether the tear is partial or complete. This is the ligament most often hurt in a common ankle sprain.
What is bone marrow edema in the ankle?
It means extra fluid inside the bone. It can show up after an injury, with stress on the bone, or with arthritis. Your doctor will look at what is causing it in your case.
What is an osteochondral lesion of the talus?
It is an injury to the cartilage and the bone underneath it on the talus, the bone that forms the main ankle joint. The report may describe its size and whether any piece looks loose.
What is a high ankle sprain?
It is an injury to the syndesmosis, the ligaments that hold the lower tibia and fibula together above the ankle joint.
Does an ankle MRI always need contrast?
No. Many ankle MRIs are done without contrast. Your doctor decides if contrast is needed for your exam.
Who should explain my ankle MRI results?
The doctor who ordered your MRI. They know your history and exam and can explain your options.
Related reading
Schedule an MRI at Millenium MRI
If your doctor has ordered an ankle MRI, Millenium MRI can help. Our scans are read by board-certified radiologists and performed by ARRT-certified technologists. Results are usually sent to your referring doctor within 24 hours, and same-day appointments are often available. We accept most insurance plans, workers' compensation, personal injury cases, and self-pay. We have centers in Ocala, Largo, and Tamarac, Florida, and in North Little Rock, Springdale, Jonesboro, and Marion, Arkansas, open Monday through Friday, 9am to 5pm.
This article is for general information and is not medical advice. Talk with your doctor about your specific situation.
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