1. We use a checklist when evaluating an MRI of the Ankle:
• Bones: screen on fat-sat images for bone marrow edema.
• Joints: screen for effusion and look at the joint capsule for
thickening.
• Ligaments: check the syndesmosis, the lateral and medial
ligaments.

2. MRI ANKLE

3. • Tendons: check the tendons using the four quadrant approach;
• Flexors on the medial side.
• Achilles tendon posteriorly.
• Peroneal tendons on the lateral side.
• Extensors on the anterior side.

4. Bones
• Start exam with fat-sat images of the bones to screen for
edema.
Bone marrow edema is only an indication that there is
something abnormal in the bone or connected structures.

5. This patient has bone marrow edema
on the posterior side of the distal tibia.
On the axial image, the edema
is localised around the insertion
site of the posterior
syndesmosis.
This is edema due to a
ligamentous avulsion injury.

6. • The patient on the left has bone marrow edema in the
medial malleolus.
• The patient on the right has edema in the medial talus.
• Both patients have had an eversion injury, with
stretching of the deltoid ligament.
• The bone marrow edema in these patients is due to
avulsion injury on the insertion sites of the deltoid
ligament.

7. • Patient has bone marrow edema in both the medial malleolus and
the medial talus.
• The lateral ligaments also show edema and thickening.
The bone marrow edema is likely due to impaction of talus and
medial malleolus secondary to inversion injury.

8. Stress fractures
• Stress fractures of the calcaneus are a frequently
unrecognized source of heel pain.
• Stress fractures are easy to miss on MR alone and this
could lead to a wrong diagnosis like for instance
osteomyelitis.

9. • This patient has edema in the calcaneus as a result of a
stress fracture.
• This injury usually results from overuse, especially in
runners.
• When the fracture is not seen on the T2W fat-sat images,
look at the non-fat-sat T2W or the T1W- images for a
hypointense fracture line.

10. • Sometimes the fracture line is not seen on MR.
• In those cases you may consider a CT-scan which
can be more sensitive.
• This patient has multiple stress fractures of the
calcaneus.

11. In this patient there is very subtle edema in the
distal fibula.
No fracture line is visible.
There is subtle thickening of the cortex and some
infiltration of the sub-periosteum.
When there is edema like in this case and no
visible fracture line, you may consider CT.

12. • In this case there is a lot of edema in the navicular bone.
• The axial image nicely depicts the stress fracture.

13. OCD
• OCD is an abbreviation which can stand for either
Osteochondritis Dissecans or Osteochondral Defect.
• Osteochondritis dissecans is used when the patient is young
and the cause is not exactly known, yet most probably due
to repetitive microtrauma.
• Osteochondral defect is mainly used when a patient is older
or when a particular trauma is thought to be the cause of
the defect.
• Both describe a joint defect which involves the articular
cartilage and the underlying subchondral bone.

14. When a small defect in the chondral plate is present, the intraarticular fluid will erode the subchondral bone, which will result in bone
marrow edema.
This process can evolve into cyst formation.
Finally, when fluid flows underneath the defect, the OCD can become unstable and may result in a corpus liberum.

15. Os Trigonum
• In the foot and ankle many accessory ossicles can be
seen.
• The most common ossicle is the os trigonum, which is a
prominent unfused apophysis of the lateral tubercle of
the talus.
• The os trigonum is present in the normal population in
about 5-15%.

17. • Compression of the os trigonum and surrounding soft tissues between the
tibia and the calcaneus during plantar flexion can be a cause of posterior
impingement.
This is especially seen in ballet dancers.
• The term Stieda process is used, when the lateral tubercle is very prominent.
This can also lead to posterior impingement.

19. This case is shown to demonstrate the great variety of
ossicles and tubercles on the posterior side of the talus.
This patient has an unfused prominent lateral tubercle with a
fibrous connection to the talus, therefore it is a partly fused os
trigonum.
On the axial image more unfused prominent tubercles on
both the medial and lateral side of the lateral tubercle are
seen.

20. Joints
• Effusion
• The left image shows a normal
fluid accumulation in the
tibiotalar joint, talocalcaneal
joint (retrocalcaneal bursa.)
• The right image shows massive
joint effusion as a reaction to
degenerative osteochondral
defects in the tibiotalar joint.
The effusion can run alongside
the flexor hallucis longus tendon
(FHL), since this tendon sheath is

22. Capsular thickening
• The ankle joint is lined by the joint
capsule.
• When the capsule is thickened, it
may cause impingement or
synovitis, which can be seen in the
image in the middle.
• The capsule thickening can be
posttraumatic or postoperative.
• On the right a patient who
developed postoperative fibrosis
after resection of a Haglund
exostosis.
There is fibrosis along the posterior
calcaneus and the posterior joint
capsule.

23. In this patient there is only a small effusion in the ankle joint.
On the non fatsat images there is subtle thickening of the capsule,
with reactive changes in the surrounding soft tissue.
This patient had anterior ankle pain due to impingement by the
thickened capsule.

24. • Capsular thickening and soft tissue
abnormalities are usually better seen on
non-fat-sat images.
• On the fat-sat images, you may think that
some edema in the subcutaneous fatty
• On the non fat-sat images however, there
thickened fibrotic tissue on the anterior

25. 1st image there is fibrous thickening of the capsule (arrow).
This patient has secondary degenerative changes in the joint with
subchondral edema and cyst formation.
It is a result of repetitive impaction of the fibrotic tissue on the bone
during dorsal flexion.

26. Ligaments
• The syndesmoses are best seen on axial images:
• Anterior tibiofibular ligament or anterior syndesmosis
• Posterior tibiofibular ligament or posterior syndesmosis
• Membrana interossei, which runs all the way up to the
fibular head.

27. Ligaments

29. Anterior syndesmosis
• In A - a normal anterior syndesmosis is seen as
a thin low intensity band.
• In B - the anterior syndesmosis is thickened
with edema, indicating partial tearing or grade 2
injury.
• In C - the anterior syndesmosis is thickened
and there probably is a focal discontinuity
(arrow) and that is the reason why this was
called a grade 3 injury (full thickness tear).
• Isolated injury of the anterior syndesmosis can
be seen in low grade exorotation injuries.

30. Posterior syndesmosis
Acute injury presents as edema and thickening,
while an old injury presents with thickening and
low signal intensity due to scar formation.
In A there is edema and thickening around the
anterior and posterior syndesmosis (arrow),
indicative of acute grade 2 injuries.
In B there is edema and thickening of the
posterior syndesmosis, which is an acute grade 2
injury.
The anterior syndesmosis is also thickened but
shows low signal.
This is scar formation as a result of prior injury.
In C there is scar tissue as a result of previous
injury, which again can be a cause of posterior
impingement.

31. There are three ligaments on the lateral side:
1.anterior talofibular ligament (ATFL)
2.calcaneofibular ligament (CFL)
3.posterior talofibular ligament (PTFL).

32. ATFL
• The ATFL runs from the lateral malleolus anteriorly to the
lateral border of the talus.
It has a transverse orientation and is best seen on axial
images.
• This is the most commonly injured ligament of the ankle
and it is also the first to be injured on the lateral side.
This means that when the CFL or the PTFL are injured, it is
very likely that the ATFL is injured aswell.

33. Here we see three patients with ATFL injury.
The patient on the left has subtle edema around the ATFL-ligament, while the ligament itself looks normal.
This probably represents a mild strain (grade 1).
Usually this is best appreciated on fatsat images.
The patient in the middle has thickening and architecture distortion representing a partial tear (grade 2).
The patient on the right has a full thickness tear (grade 3).

34. Bright rim sign
This sign presents as a fine linear band of high
which is the result of a small avulsion of
grade 3 full thickness tear.
Here an example of a grade 3 ATFL tear with a
(arrow).
It is thought that it is caused by a chemical
subcortical fatty marrow is exposed to joint

35. CFL
• The Calcaneofibular ligament runs from the distal fibula
to the lateral side of the calcaneus and is best appreciated
on coronal images.
• The CFL passes two joints, the talocrural joint and the
talocalcaneal joint.
• Isolated injury of the CFL is uncommon.
Most of the time the ATFL is injured as well.

36. PTFL
• The Posterotalofibular ligament courses posterior to the
lateral tubercle on the posterior aspect of the talus.
• Isolated injury is very rare.
When it is injured, there has to be injury to the other
lateral ligaments.

37. Deltoid ligament
• The deltoid ligament is best evaluated in the
coronal plane.
The deep layer connects the inferior border of
the medial malleolus to the medial side of the
talus.
The fibers are interposed with fatty tissue,
giving it a striped pattern on MR.
• The superficial layer of the deltoid ligament is
connected to the navicular bone anteriorly and
the calcaneus posteriorly.
At the insertion on the medial malleolus, it
blends with the periosteum of the medial
malleolus and the flexor retinaculum.

38. These images show injury to the deep deltoid ligament.
It is difficult to differentiate between grade 1 and 2 injuries, because the edema will blur the normal striped pattern.
The image on the right shows fiber discontinuity making it a full thickness or grade 3 tear.

39. Plantar fascia
• The plantar fascia is a thick aponeurosis which supports
the arch on the plantar side of the foot.
It runs from the tuberosity of the calcaneus to the heads
of the metatarsal bones.
• Plantar fasciitis, the most common cause of heel pain in
the athlete, is a low-grade inflammation involving the
plantar aponeurosis and the perifascial structures.

40. MR can show edema around the insertion of the plantar fascia on the calcaneus and spurring.
When the patient is treated, the edema will vanish, but the spurring may still be present.
Spurring as seen on a X-ray therefore can be seen in symptomatic and asymptomatic patients.

41. Tendons
• Anatomy in the axial plane
• The tendons can be divided into four compartments:
• Medial: (from medial to lateral: Tom-Dick-Harry)
• Tibialis Posterior (PTT)
• Flexor Digitorum
• Flexor Hallucis Longus
• Posterior
• Achilles
• Plantaris
• Lateral
• Peroneus Longus

43. • Tendinopathy is a collective term to describe different tendon disorders like
tendinosis, tendinitis and mucoid degeneration.
• The pathogenesis of these disorders is different, but the clinical presentation
and imaging features are not always distinctive.
Therefore it is best just to describe a tendon abnormality as tendinopathy
without trying to further specifying the abnormality.

44. • MR findings in tendinopathy are:
• Thickening
• Abnormal signal
• Tenosynovial fluid
• Most tendons in the ankle joint have a tenosynovial layer.
A small amount of fluid around the tendon therefore can be normal.
The amount of fluid should not exceed the volume of the tendon itself.
• The achilles tendon does not have a tenosynovial layer but a paratenon.
Fluid around the Achilles tendon is always abnormal.

45. TIBIALIS POSTERIOR TENDON
• The posterior tibial tendon is the most commonly injured tendon.
Tendinopathy is seen as abnormal swelling of the tendon, but you have to
realize, that the normal posterior tibial tendon can measure twice the size of
the flexor digitorum tendon.

46. Posterior tibial tendon dysfunction is more common in women
and in people older than 40 years of age.
It results in pain and swelling on the medial aspect of the ankle
and an acquired flatfoot deformity.
Posterior tibial tendon injury in young patients is mainly due to
trauma or overuse.
When the posterior tibial tendon is injured, be sure to check the
spring ligmanent, since they together maintain the arch of the foot
on the medial side.
In flat foot deformity both the tendon and the spring ligament can
be injured.

47. Achilles tendon
The Achilles tendon is the largest and
strongest tendon in the human body.
The two most common injuries are
tendinopathy and rupture.
Achilles tendinopathy is most likely due to
a series of microtears that weaken the
tendon and cause swelling of the tendon
(image on the right).

48. On sagital images the achilles tendon should be a
straight line without any fluid around it and no focal
thickening.

49. Three fat sat axial images of the achilles tendon.
•Left-Normal achilles tendon. Its border is concave, it is within
7mm, no paratenon fluid is seen.
•Middle- Normal achilles tendon. Note that the other tendons all
contain fluid, but the achilles paratenon shows no fluid at all.
•Right-Fluid alongside the paratenon, i.e. paratenonitis and
achilles tendinopathy.

50. Normally, a small amount of fluid is seen in the retrocalcanear
bursa.
Too much fluid is indicative of bursitis.
Thickening of the Achilles is seen with paratenonitis.
The Haglund syndrome consists of the triad of:
1.Haglunds exostosis
2.Retrocalcaneal bursitis
3.Achilles insertional tendinopathy

51. This image shows an extreme case of insertion
tendinopathy of the Achilles tendon.

52. Rupture of the Achilles tendon usually occurs in the part of the tendon situated within 6 centimeters of the insertion to the
calcaneus.
This part is prone to rupture because the blood flow in this area is poor, which also can impair its ability to heal.
The image shows an old rupture.

53. Peroneal tendons
• The peroneus brevis tendon is injury-prone, because it is
positioned in between the fibula and peroneus longus
tendon.
• As the foot undergoes dorsiflexion, the peroneus brevis
tendon is repeatedly compressed between the peroneus
longus tendon and the lateral malleolus, predisposing to
tear.
• Once a small tear is initiated, it will results in a cashew
nut deformity.
The peroneus longus tendon migrates forward into the
peroneus brevis tendon tear, thereby preventing healing.

55. In the middle and right we see two examples of
cashew nut deformity, indicative of partial split
rupture.
This can be challenging, because the actual tear
cannot be seen, only the architectural deformation.

56. • Standard axial, coronal and sagittal planes are used in the ankle both on 1.5T
and in 3T.
• In addition to the standard planes, a oblique scan is sometimes included
oriented perpendicular to the peroneus and tibialis posterior tendons.
Small tears or subtle tendinopathy are better visualized on these views.
• The orientation of the tendons along the medial and lateral malleolus can
cause the 'magic angle artifact' to occur.
The tendons will show relatively hyperintense signal at 55* to B0), simulating
pathology like tendinopathy or partial tears.
• This artifact is visible on short TE images (f.e. PD).
On long TE images (like T2) this artifact does also occur but less pronounced.