Vol 9, No 3, May/June 2001
187
Magnetic resonance (MR) imaging
of the foot and ankle has lagged
behind MR imaging of other joints
in clinical acceptance and utility,
because of the complex anatomy of
the foot and ankle and the need for
small-field-of-view, high-resolution
images. Recent advances in both
hardware and software, however,
have made possible the acquisition
of high-resolution images. This
feature, combined with the degree
of soft-tissue contrast that can be
achieved with MR imaging and the
ability to obtain images in multiple
planes, has led to the increasing
importance of this modality in
imaging of the foot and ankle for
both diagnosis and surgical plan-
ning. It is important that physi-
cians understand the common clin-
ical MR imaging techniques and
their role in evaluating disorders
of the foot and ankle to most effec-
tively utilize this diagnostic mo-
dality.
Technique
Because of the complex anatomy of
the foot and ankle and the small

hindfoot, the midfoot, and the fore-
foot.
1
The midfoot is adequately
examined by imaging both the
hindfoot and the forefoot; there-
fore, examination protocols can be
further simplified into two zones:
ankle-hindfoot and forefoot.
To image the hindfoot and ankle,
the patient is placed in a supine
position with the medial malleolus
centered in the coil. The foot is
allowed to rest in a relaxed posi-
tion, generally in 10 to 20 degrees of
plantar-flexion and 10 to 30 degrees
of external rotation. The foot posi-
tion may need to be altered when
imaging specific ligaments, such as
the calcaneofibular ligament. For
forefoot examinations, the patient
can be either supine or prone with
Dr. Recht is Section Head, Outside Imaging,
Department of Diagnostic Radiology, Cleve-
land Clinic Foundation, Cleveland, Ohio. Dr.
Donley is Staff Surgeon, Department of Ortho-
paedic Surgery, Cleveland Clinic Foundation.
Reprint requests: Dr. Recht, Department of
Diagnostic Radiology, Cleveland Clinic
Foundation, A21, 9500 Euclid Avenue,

planes provide the greatest amount
of information.
A variety of pulse sequences can
be utilized in the examination of the
foot and ankle. T1-weighted (short
repetition time [TR]/short echo time
[TE]) SE images provide excellent
anatomic detail and information
about the integrity of the bone mar-
row. T2-weighted (long TR/long
TE) SE images allow detection of the
increased water content seen with
most pathologic processes as abnor-
mal high signal intensity. Fast SE
T2-weighted sequences have largely
replaced conventional SE T2-weighted
sequences because of the ability to ob-
tain images in a shorter time period
with higher resolution. Gradient-
echo sequences allow the acquisition
of thin contiguous sections that can
be reformatted in multiple planes.
These sequences have been shown
to be useful in the detection of carti-
lage abnormalities.
2,3
Short-tau inversion recovery
(STIR) imaging is a method of fat
suppression that has proved very
sensitive in detecting marrow ab-

5,6
The foot and ankle can be im-
aged with high-field-strength (>0.5-
T) or low-field-strength (≤0.5-T)
magnets. A high-field-strength
MR Imaging of the Foot and Ankle
Journal of the American Academy of Orthopaedic Surgeons
188
Definitions of Radiologic Terms
Chemical-selective The use of chemically selective radio-frequency
fat suppression pulses to eliminate fat signal by taking advantage
of the difference in resonance frequency between
fat and water protons
Echo time (TE) The time between the middle of the excitation pulse
and the middle of the spin echo
Gradient-echo (GRE) Describing a sequence in which an echo is produced
by a single radio-frequency pulse followed by a
gradient reversal
Proton-density- An image acquired with a long TR (e.g., 2,000-3,000
weighted image msec) and a short TE (e.g., 20 msec) to emphasize
differences in proton density and minimize T1 and T2
differences between tissues
Repetition time (TR) The time between successive excitations of a section
Short-tau inversion Describing a sequence that suppresses fat signal by
recovery (STIR) the use of a 180-degree inversion pulse and a short
inversion time
Spin-echo (SE) Describing a sequence in which an echo is produced
by a 90-degree radio-frequency pulse followed by
one or more 180-degree radio-frequency pulses
T1 Spin-lattice or longitudinal relaxation time. The

and flexor hallucis longus medially;
and the tibialis anterior, extensor
digitorum longus, extensor hallucis
longus, and peroneus tertius anteri-
orly. Tendons are composed primar-
ily of collagen, elastin, and reticulin
fibers.
Normal tendons appear as ho-
mogeneous low signal intensity on
MR imaging because of their lack
of mobile protons.
7
However, on
T1-weighted and proton-density-
weighted (long TR/short TE) im-
ages, normal tendons can have inter-
mediate signal intensity because of
the “magic angle effect.”
8
This effect
occurs with short-TE sequences
because the signal intensity of struc-
tures with poorly hydrated protons,
such as tendons, depends in part
on the orientation of the structure
in relation to the main magnetic
field. When a structure is oriented
obliquely in relation to the main
magnetic field, its signal intensity is
increased on short-TE sequences;

images (obtained with the same sec-
tion thickness and positions to allow
comparison), coronal T1-weighted,
and sagittal fat-suppressed fast SE
T2-weighted sequences. A sagittal
T1-weighted sequence is added
when examining the Achilles tendon.
Pathologic changes that can be
seen in and about tendons on MR
imaging include tenosynovitis,
tendinopathy, and tendon tears.
Tenosynovitis is best visualized on
T2-weighted images as high-signal-
intensity fluid surrounding a normal-
appearing tendon (Fig. 3). “Ten-
dinopathy” or “tendinosis” is the
term currently favored to describe
tendons that are abnormal but not
torn. Although some authors still
use the term “tendinitis,” studies
have not shown a true inflammatory
process in tendons.
9,10
Rather, histo-
logic studies have demonstrated
hyperplasia, fibrosis, and vacuolar,
mucoid, eosinophilic, and fibrillary
degeneration. On MR imaging,
tendinopathy is characterized by
altered tendon morphology, usual-

FH
PL
PB
EH
ED
Figure 2 True transaxial images of the
peroneal tendons. The sections are graphi-
cally prescribed off a sagittal image as the
tendons curve around the ankle.
Type 1 is characterized by hypertro-
phy of the tendon with partial tears
oriented primarily longitudinally.
The tendon is enlarged (Fig. 4, A),
with foci of increased signal inten-
sity on T2-weighted and STIR images
(Fig. 4, B). Type 2 is characterized
by a partially torn atrophic tendon;
the appearance is of a small tendon
with foci of increased signal intensi-
ty on T2-weighted or STIR images
(Fig. 4, C). Type 3 tears are com-
plete tendon ruptures (Fig. 4, D).
Although all of the tendons of the
foot and ankle can be studied with
MR imaging, the tendons most
often associated with injury or dis-
ease are the Achilles, tibialis poste-
rior, and peroneal tendons.
Achilles Tendon
The Achilles tendon is the largest

and proton-density-weighted im-
ages, but the signal usually de-
creases in intensity on T2-weighted
and STIR images. Although mea-
surements of the thickness of the
Achilles tendon have been pub-
lished (normal, <8 mm),
1
careful
assessment of the anterior margin
of the tendon on transaxial views
may be more useful. Loss of the
normal concave margin of the ante-
rior aspect of the tendon is a sign
that the tendon is thickened and
abnormal.
MR Imaging of the Foot and Ankle
Journal of the American Academy of Orthopaedic Surgeons
190
Figure 3 Tenosynovitis of the flexor hallu-
cis tendon. Note the high-signal-intensity
fluid (arrows) surrounding the normal
low-signal-intensity tendon and the metal-
lic artifact about the tibia secondary to pre-
vious hardware placement.
Figure 4 Patterns of tendon rupture. A, Type 1 tear of the tibialis posterior tendon. Transaxial T1-weighted image at the level of the
sustentaculum tali demonstrates an enlarged, irregularly shaped tibialis posterior tendon (arrow). B, Transaxial STIR image of the same
ankle demonstrates high signal intensity within the enlarged tibialis posterior tendon (arrows). C, Type 2 tear of the tibialis posterior ten-
don. Transaxial T1-weighted image demonstrates a small atrophic tibialis posterior tendon (white arrows) approximately half the diame-
ter of the flexor digitorum tendon (black arrow). D, Type 3 tear of the Achilles tendon. Sagittal T2-weighted fast SE image demonstrates

commonly seen in middle-aged
women, who present with an ac-
quired, painful flatfoot; these are
generally chronic tears.
11,12
The tib-
ialis posterior tendon is the most
medial tendon in the posterior com-
partment at the level of the ankle.
The tendon continues into the foot,
where it inserts onto the navicular,
Michael P. Recht, MD, and Brian G. Donley, MD
Vol 9, No 3, May/June 2001
191
A
C
E
B
D
F
Figure 5 A and B, Normal Achilles ten-
don. A, On T1-weighted sagittal image,
the normal Achilles tendon is of homoge-
neous low signal intensity and has sharp
interfaces with the surrounding soft tissue.
B, Transaxial T1-weighted image at the
level of the distal Achilles tendon. The
concave anterior surface of the tendon
gives a crescentic shape to the distal por-
tion (arrowheads). C and D, Chronic

by an enlarged tendon, which may
be four to five times the size of the
flexor digitorum tendon (Fig. 4, A
and B). There is increased signal
intensity within the tendon on short-
TE images, which often remains
high on T2-weighted and STIR
images. Type 2 tears present as a
smaller than normal tendon, often
the same size as or smaller than the
flexor digitorum longus (Fig. 4, C).
Type 3 tears are complete tendon
ruptures.
Peroneal Tendons
The peroneus longus and brevis
tendons occupy a common synovial
sheath up to the level of the calca-
neocuboid joint, beyond which the
sheath bifurcates. At the level of the
lateral malleolus, the peroneus bre-
vis tendon is anteromedial or ante-
rior to the peroneus longus tendon.
The posterior edge of the fibula is
normally concave in this region,
forming a groove within which the
tendons lie. The tendons are kept
within this groove by the superior
peroneal retinaculum.
On MR imaging, normal peroneal
tendons are of similar size and ho-

A). There may or may not be in-
creased signal intensity within the
tendon. An osseous ridge at the lat-
eral margin of the fibula has been
associated with a split peroneus bre-
vis tendon, and is considered to rep-
resent changes secondary to repeti-
tive subluxation of the peroneal ten-
dons.
13
Other MR findings that are
associated with, and may predispose
to, splitting of the peroneus brevis
MR Imaging of the Foot and Ankle
Journal of the American Academy of Orthopaedic Surgeons
192
A B C
Figure 6 Lesions of the peroneal tendons. A, Transaxial T1-weighted image obtained just distal to the lateral malleolus demonstrates a
completely bisected peroneus brevis tendon (arrowheads). T1-weighted transaxial (B) and coronal (C) images show subluxation of the
peroneal tendons (arrows) so that they lie lateral to the malleolus, rather than posterior to it.
tendon include a flat or convex fibu-
lar groove, a ligamentous tear, or
the presence of a peroneus quartus
muscle or the low-lying belly of the
peroneus brevis muscle.
14
Traumatic peroneal subluxation
or dislocation is associated with dis-
ruption of the superior retinaculum
or stripping of the periosteum at its

grouped into three complexes: the
lateral complex, consisting of the
anterior talofibular, posterior talo-
fibular, and calcaneofibular liga-
ments; the deltoid ligament, which
has several components; and the
syndesmotic complex, composed of
the interosseous membrane, the
anterior and posterior tibiofibular
ligaments, and the transverse tibio-
fibular ligament. To evaluate these
ligaments with MR imaging, it is
necessary to image them in a plane
parallel to their long axes. This
plane varies for the different liga-
ments, but a cadaveric study of the
ankle ligaments demonstrated that
particular planes were optimal for
studying the various ligaments.
16,17
The transaxial plane with the foot
positioned in 10 to 20 degrees of
dorsiflexion provides the best visual-
ization of the anterior and posterior
talofibular ligaments; the anterior,
Michael P. Recht, MD, and Brian G. Donley, MD
Vol 9, No 3, May/June 2001
193
A
C

complexes need to be imaged. The
MR sequences used to evaluate the
ankle ligaments include T1-weighted
SE, T2-weighted fast SE, and STIR
sequences. In cases of chronic ankle
instability, MR arthrography may
also be useful.
Normal ligaments are thin and of
low signal intensity on all MR pulse
sequences. Occasionally, they have
a striated appearance, especially the
deltoid and posterior talofibular
and tibiofibular ligaments.
18
Be-
cause of the oblique course of the
tibiofibular ligaments, the talus may
be seen on images demonstrating
their fibular attachments. This can
lead to misidentification of the
tibiofibular ligaments as the talo-
fibular ligaments. The best way to
avoid this mistake is to identify the
insertion of the ligaments. The
shape of the talus and the fibula in
the transaxial plane can also be used
to correctly identify the two sets of
ligaments.
8
At the level of the tibio-

This
is because the torn, scarred ligament
is closely applied to the bone and is
better visualized when separated
from the bone by the intra-articular
injection of contrast material (Gd-
DTPA). In addition, contrast extra-
vasation through the torn ligament
into the surrounding soft tissues
serves as convincing evidence of dis-
ruption of the ligament.
Bones
Infection
Infection of the bones of the foot
and ankle occurs most commonly in
diabetic patients, usually due to
direct extension of soft-tissue infec-
tion. Magnetic resonance images,
especially STIR and fat-suppressed
T1-weighted images acquired after
intravenous contrast administration
effectively depict the bone marrow
changes that occur with osteomye-
litis.
19
However, these changes are
not specific for osteomyelitis. The
differentiation of bone marrow
changes due to infection from those
due to edema or neuropathy has

are acquired in at least two planes,
which are determined on the basis
of the site of the suspected infection.
Fractures
Magnetic resonance imaging has
little role to play in the evaluation of
acute traumatic bone injuries, as
they are usually easily diagnosed on
conventional radiography. How-
ever, MR imaging may be useful in
MR Imaging of the Foot and Ankle
Journal of the American Academy of Orthopaedic Surgeons
194
Figure 8 Chronic tear of the anterior
talofibular ligament. This transaxial T2-
weighted image demonstrates the absence
of the anterior talofibular ligament, with
high-signal-intensity fluid (arrows) filling
the expected location of the ligament.
identifying bone contusions, occult
nondisplaced fractures, and stress
fractures and stress reactions in the
foot and ankle. Metatarsal stress
fractures can generally be diag-
nosed without MR imaging. In con-
trast, stress fractures of other tarsal
bones, such as the navicular, cunei-
forms, and calcaneus, often present
as foot pain of unknown etiology. If
conventional radiographs appear

intensity on STIR sequences. They
can be differentiated from fractures
by the lack of a linear component.
Stress responses appear similar to
bone bruises but can be differen-
tiated from them by the lack of an
antecedent acute traumatic event.
Osteochondral Injuries
of the Talar Dome
Osteochondral injuries of the
talar dome occur most commonly in
the second to fourth decades of life
and affect both the medial and lat-
eral aspects of the dome.
23
Most
lesions are apparent on conventional
radiographs; however, MR imaging
can depict lesions too small to be
seen on plain films and may be use-
ful in evaluating the extent of the
lesion and the stability of the frag-
ment.
23
Increased signal intensity
separating the lesion from the un-
derlying bone on T2-weighted or
STIR images is the most frequent
MR sign of instability, but this ap-
pearance has also been reported in

Figure 9 Osteomyelitis of the calcaneus. A, Sagittal T1-weighted image demonstrates a
soft-tissue ulcer (white arrow) on the plantar surface of the foot adjacent to the area of
abnormal low signal intensity within the calcaneus (black arrows). B, Sagittal fat-
suppressed T1-weighted image shows enhancement (arrows) of the calcaneus and adjacent
soft tissues, as well as subtle cortical disruption (lower arrow).
Figure 10 Stress fracture of the navicular.
Coronal T2-weighted image demonstrates
high signal intensity within the navicular
surrounding a thin linear area of low signal
intensity (arrowheads), which represents
the fracture line.
evaluation of talar cartilage has
been more difficult, even with both
sagittal and coronal images, because
the talar cartilage is considerably
thinner.
Bone Tumors
Although MR imaging is very
sensitive in the detection of bone
tumors, it frequently lacks specific-
ity. However, MR imaging can be
useful in evaluating the extent of
the tumor and the presence of an
associated soft-tissue mass. The
imaging is done in all three planes
with a combination of T1-weighted
SE, STIR, and T2-weighted fast
SE sequences. Occasionally, a fat-
suppressed T1-weighted sequence
is used after administration of in-

thick and of homogeneously low
signal intensity on all pulse se-
quences.
27
In patients with plantar
fasciitis, the plantar fascia is thick-
ened (7 to 8 mm thick) and demon-
strates areas of increased signal
intensity on T2-weighted and STIR
sequences
4,27
(Fig. 12). There fre-
quently is also abnormally increased
signal intensity in the adjacent sub-
cutaneous tissue. Increased signal
intensity may also be seen in the cal-
caneus at the insertion site of the
plantar fascia, presumably second-
ary to reactive edema.
Plantar fasciitis is a clinical diag-
nosis and rarely, if ever, warrants
MR imaging. However, in patients
with a painful heel syndrome, it can
occasionally be helpful in excluding
other etiologic possibilities, such as
calcaneal stress fractures and tarsal
tunnel masses.
Plantar Fibromatosis
Plantar fibromatosis is character-
ized by fibrous proliferation in the

characteristic, presenting as single
or (less commonly) multiple nod-
ules in the subcutaneous tissues of
the plantar aspect of one or both
feet. The dorsal margin of the lesion
is usually ill defined, but the plantar
margin is well defined against the
subcutaneous fat. The nodules typi-
cally are less than 3 cm in size. On
T1-weighted images, the masses are
usually isointense to slightly hypo-
intense to skeletal muscle; they
remain of intermediate to minimally
increased signal intensity on T2-
weighted images
28
(Fig. 13). On
STIR imaging, the nodules can be of
increased signal intensity (hyperin-
tense to skeletal muscle). After in-
travenous contrast administration,
there is variable enhancement.
Interdigital Neuroma
Interdigital (Morton’s) neuroma
(Fig. 14) is a benign, nonneoplastic
condition consisting of perineural
fibrosis, most likely due to entrap-
ment.
29
The lesions most commonly

The lesions remain of low signal
intensity on T2-weighted images,
which allows their differentiation
from true neuromas, synovial cysts,
and fluid-filled intermetatarsal bur-
sae. They frequently have increased
signal intensity on STIR images,
and there is variable enhancement
after administration of intravenous
contrast material.
Tarsal Tunnel Syndrome
Tarsal tunnel syndrome (Fig. 15)
is caused by entrapment of the pos-
terior tibial nerve and its branches
(i.e., the medial and lateral plantar
nerves) within the tarsal tunnel, a
fibro-osseous tunnel that lies be-
neath the flexor retinaculum on the
medial side of the foot. The floor of
the tarsal tunnel is osseous and is
formed by the medial surface of the
talus, the sustentaculum tali, and the
medial wall of the calcaneus. The
Michael P. Recht, MD, and Brian G. Donley, MD
Vol 9, No 3, May/June 2001
197
Figure 13 Plantar fibromatosis. T1-weighted (A) and T2-weighted (B) coronal images
demonstrate a mass (arrowheads) associated with the plantar fascia. The mass is isoin-
tense to skeletal muscle on the T1-weighted image and remains of low signal intensity on
the T2-weighted image. There is a marker on the plantar aspect of the foot to identify the

Summary
Magnetic resonance imaging of the
foot and ankle is playing an in-
creasingly important role in the
diagnosis of a wide range of foot
and ankle abnormalities and the
planning for their surgical treat-
ment. It is important to obtain
high-resolution images of the foot
and ankle in multiple planes with
the use of appropriate pulse se-
quences. When this is accom-
plished, disorders of tendons, liga-
ments, bone, and soft tissue can be
accurately diagnosed.
MR Imaging of the Foot and Ankle
Journal of the American Academy of Orthopaedic Surgeons
198
A B
Figure 15 Space-occupying lesion of the tarsal tunnel. A, T1-weighted transaxial image
demonstrates an intermediate-signal-intensity mass (arrows) within the tarsal tunnel, rep-
resenting lymphoma. B, T2-weighted transaxial image demonstrates a multiseptate high-
signal-intensity mass (arrows) within the tarsal tunnel, representing a ganglion.
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