Ankle MRI is one of the most common musculoskeletal studies a technologist will run, and reading it well starts with knowing the normal bones and tendons cold. This reference walks through every structure in our ankle flashcard deck across the three standard planes (axial, sagittal, and coronal), with a plain-language definition, how each structure looks on MRI, and the pathology you will actually run into at the scanner.
The osseous framework of the ankle and hindfoot. Cortical bone is dark on every sequence; the marrow inside is bright on T1 and darkens on fat-suppressed fluid sequences.
The larger, weight-bearing leg bone whose lower end forms the roof and medial wall of the ankle joint.
On MRI: On midline sagittal it is the long bone above the talus, with bright fatty marrow on T1 and a thin dark cortex. The distal tibial plafond articulates with the dome of the talus.
Common pathology: Distal tibial (plafond/pilon) fractures, marrow edema from bone bruise or stress reaction, and osteomyelitis show bright signal on fluid-sensitive sequences.
The slender lateral leg bone that runs alongside the tibia and forms the lateral malleolus at the ankle.
On MRI: Seen lateral to the tibia, smaller in caliber, with fatty marrow on T1; on sagittal it parallels the tibia and tapers into the lateral malleolus.
Common pathology: Distal fibular fractures (the most common ankle fracture), stress fractures in runners, and marrow edema.
The keystone hindfoot bone that sits between the tibia/fibula above and the calcaneus below, transmitting body weight to the foot.
On MRI: Central in every plane: its dome articulates with the tibial plafond, its body sits on the calcaneus, and its head points toward the navicular. Fatty marrow is bright on T1.
Common pathology: Osteochondral lesions of the talar dome (medial more than lateral), avascular necrosis, and talar neck fractures.
Tip: The talus has no muscular attachments; trace it as the bone wedged between the tibial plafond above and the calcaneus below.
The heel bone, the largest tarsal bone, forming the back of the foot and the attachment point for the Achilles tendon.
On MRI: The large bone at the back of the foot on sagittal, with abundant fatty marrow on T1. The Achilles tendon inserts on its posterior tuberosity.
Common pathology: Calcaneal stress fractures, marrow edema, and bone bruises; insertional changes where the Achilles and plantar fascia attach.
The boat-shaped midfoot bone between the talar head behind it and the three cuneiforms in front of it.
On MRI: Sits just distal to the talar head on sagittal, with a concave proximal surface; fatty marrow on T1.
Common pathology: Navicular stress fractures (notoriously slow to heal in athletes), accessory navicular, and Kohler disease in children.
The cube-shaped lateral midfoot bone between the calcaneus behind it and the fourth and fifth metatarsals in front.
On MRI: Found on the lateral side of the midfoot; on axial it sits lateral to the navicular and cuneiforms. The fibularis longus tendon grooves its undersurface.
Common pathology: Cuboid stress fractures, the nutcracker fracture from compression, and cuboid syndrome.
The largest of the three cuneiform bones, sitting on the medial side of the midfoot and articulating with the first metatarsal.
On MRI: On axial it is the most medial cuneiform, lined up between the navicular and the base of the first metatarsal. Fatty marrow on T1.
Common pathology: Lisfranc injuries, stress fractures, and degenerative change at the first tarsometatarsal joint.
Tip: Count the cuneiforms from medial to lateral: medial (largest), intermediate (middle), then lateral, each leading to its matching metatarsal.
The smallest and shortest cuneiform, set between the medial and lateral cuneiforms and articulating with the second metatarsal.
On MRI: On axial it sits between the medial and lateral cuneiforms; because it is recessed, the second metatarsal base keys into it (the Lisfranc keystone).
Common pathology: Its recessed position makes the second metatarsal base the keystone of the Lisfranc joint, a frequent injury site.
The cuneiform on the lateral side of the medial column, articulating with the third metatarsal and abutting the cuboid.
On MRI: On axial it is the most lateral of the three cuneiforms, sitting between the intermediate cuneiform and the cuboid. Fatty marrow on T1.
Common pathology: Lisfranc complex injuries, stress fractures, and midfoot degenerative change.
The short, thick long bone of the great toe ray, articulating with the medial cuneiform at its base.
On MRI: The most medial and stoutest metatarsal on axial; fatty marrow on T1 with a thin dark cortex.
Common pathology: First tarsometatarsal degeneration, fractures, and marrow edema; relevant to hallux and bunion assessment.
The long bone of the second toe ray, whose base is recessed between the cuneiforms as the anchor of the Lisfranc joint.
On MRI: Lies just lateral to the first metatarsal on axial; its base keys into the intermediate cuneiform.
Common pathology: Second metatarsal stress fractures (march fractures) and Lisfranc injuries, where a widened first-to-second metatarsal base gap is a key clue.
The bony prominence on the inner ankle formed by the distal end of the tibia.
On MRI: On axial it is the medial bony knob, with the posterior tibial, flexor digitorum, and flexor hallucis longus tendons passing just behind it. Fatty marrow on T1.
Common pathology: Medial malleolar fractures, often paired with a fibular fracture, and the deltoid ligament attachment site.
The bony prominence on the outer ankle formed by the distal end of the fibula.
On MRI: On axial it is the lateral bony knob, sitting more posterior than the medial malleolus, with the peroneal tendons curving behind it. Fatty marrow on T1.
Common pathology: Distal fibular (lateral malleolar) fractures are the most common ankle fracture; lateral collateral ligament injuries attach here.
Tip: The lateral malleolus normally sits slightly more posterior and extends slightly lower than the medial malleolus; use that asymmetry to orient left versus right.
The large posterior tendon and the sole's supporting band, both seen end-on on axial and along their length on sagittal.
The thick conjoined tendon of the gastrocnemius and soleus that inserts on the back of the calcaneus and powers plantar flexion.
On MRI: Uniformly dark on all sequences. On axial it is the large oval tendon behind the ankle with a flat or concave front edge; on sagittal it is a long dark band to the calcaneal tuberosity.
Common pathology: Tendinosis (thickening with a convex front border), partial tears, and complete ruptures roughly 2 to 6 cm above the insertion.
Tip: A normal Achilles has a flat or slightly concave anterior margin on axial; a rounded, convex front edge suggests tendinosis.
The thick fibrous band along the sole that runs from the calcaneus toward the toes and supports the longitudinal arch.
On MRI: A thin dark band hugging the bottom of the foot on sagittal, anchored at the medial calcaneal tuberosity.
Common pathology: Plantar fasciitis (thickening and bright fluid signal near the calcaneal origin), tears, and plantar fibromas.
The medial, lateral, and anterior tendons that move the ankle and foot. All are dark on standard sequences; they are easiest to count end-on as round dots on axial, then followed along their length on sagittal and coronal.
The lateral tendon group (fibularis longus and brevis) that everts the foot and runs behind the lateral malleolus.
On MRI: On axial, dark tendons curving behind the lateral malleolus inside the retromalleolar groove, sharing a common synovial sheath at that level.
Common pathology: Peroneal tendinosis, longitudinal split tears (especially of the brevis), and subluxation or dislocation out of the retromalleolar groove.
The lateral tendon that inserts on the base of the fifth metatarsal and helps evert the foot.
On MRI: Behind the lateral malleolus it lies deeper and more anterior, hugging the bone; distally it heads to the fifth metatarsal base. Dark on all sequences.
Common pathology: Longitudinal split tears are classic for the brevis, often where it wraps the lateral malleolus.
Tip: At the retromalleolar groove the brevis is the tendon sitting against the bone; the longus rides just behind it.
The lateral tendon that wraps under the cuboid to insert on the medial cuneiform and first metatarsal base, everting and plantar flexing the foot.
On MRI: Behind the lateral malleolus it lies superficial to the brevis, then turns under the cuboid toward the medial sole. Dark on all sequences.
Common pathology: Tendinosis and tears, and pathology at the os peroneum where the tendon turns under the cuboid.
The most medial flexor tendon, which supports the medial arch and inverts the foot, inserting mainly on the navicular.
On MRI: On axial it is the largest, most anterior tendon behind the medial malleolus; normally about twice the caliber of the adjacent flexor digitorum longus.
Common pathology: Posterior tibial tendon dysfunction is a leading cause of acquired adult flatfoot; look for tendinosis, splits, and tears near the navicular insertion.
Tip: Behind the medial malleolus the order front to back is Tom, Dick, and Harry: posterior Tibial, flexor Digitorum, then flexor Hallucis longus.
The largest anterior tendon, which dorsiflexes the foot and inserts on the medial cuneiform and first metatarsal base.
On MRI: The most medial and largest of the tendons crossing the front of the ankle; dark on all sequences as it runs to the medial midfoot.
Common pathology: Tibialis anterior tendinosis and ruptures, which cause a foot drop and a slap-foot gait.
The deep posteromedial tendon that flexes the great toe, running between the two tubercles of the posterior talus.
On MRI: On axial it is the most posterior of the medial flexor tendons, dark, passing through its fibro-osseous tunnel behind the talus and beneath the sustentaculum tali.
Common pathology: Stenosing tenosynovitis (dancer's tendinitis) at the posterior ankle, and pathology associated with an os trigonum.
The deep posterior calf muscle whose tendon becomes the flexor hallucis longus, flexing the great toe.
On MRI: Seen as a muscle belly in the deep posterior compartment on axial, with intermediate muscle signal that transitions into its dark tendon distally.
Common pathology: Muscle strain or edema on fluid-sensitive sequences, and the muscle-tendon junction is a landmark for posterior ankle impingement.
A standard ankle MRI shows the distal tibia and fibula, the medial and lateral malleoli, the talus and calcaneus, the midfoot bones (navicular, cuboid, the three cuneiforms) and proximal metatarsals, the Achilles tendon and plantar aponeurosis, and the medial, lateral, and anterior tendons (posterior tibial, flexor hallucis longus, the peroneal/fibularis longus and brevis, and tibialis anterior). This page labels each one with its MRI appearance.
Axial is the workhorse for counting and evaluating the tendons end-on as they pass the malleoli, and for the tendon groups behind each malleolus. Sagittal is best for the Achilles tendon, plantar fascia, and the bone alignment from tibia to talus to calcaneus. Coronal is useful for the talar dome, the malleoli, and the tibiotalar joint surfaces.
Normal tendons and ligaments are uniformly dark (low signal) on all sequences because they are dense, organized collagen. Bright fluid signal within or around a tendon on a fat-suppressed T2 or PD sequence suggests tenosynovitis, tendinosis, or a tear. Watch for the magic angle artifact, where a normal tendon curving near 55 degrees to the main field can look falsely bright on short-TE sequences.
Use the mnemonic Tom, Dick, and Harry for the tendons passing behind the medial malleolus, from front to back: posterior Tibial, flexor Digitorum longus, and flexor Hallucis longus. The posterior tibial tendon is normally the most anterior and the largest, about twice the caliber of the flexor digitorum longus next to it.
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