Imaging of foot in non trauma and non neoplastic diseases

 Radiologic evaluation of the foot is often a
complex task given the relatively small size
of structures, detailed intricacy of anatomy,
multifaceted relationships and mechanism of
the anatomic structures, and wide range of
pathologic entities.
2

Primary centers
 Within the fetal period, ossification commences first in the
metatarsals, followed closely by the distal phalanges,
proximal and finally the middle phalanges.
 this is a different order from that found in the hand,
where the distal phalanges are the first to commence
ossification.
 The primary centres for the shafts of the metatarsals
appear between 8-10 prenatal weeks, which is at a similar
time to that for the metacarpals.
 Metatarsals 2 -4 tend to appear before metatarsal 5, while
the first metatarsal may not appear until 12 prenatal
weeks.
 The distal phalanges appear around the end of the 2nd
and throughout the 3rd month of intra-uterine life and so
may appear- before the shaft of the first metatarsal.
4The Juvenile Skeleton, By Louise Scheuer, Sue Black

 The primary centres of ossification for the proximal
phalanges appear in the 4th prenatal month, around
14-16 prenatal weeks.
 The centres for the first to the third toes tend to
appear in advance of those for the fourth and fifth toe.
 As with the hand, the middle phalanges of the foot are
the last of the long bones to commence ossification.
 In summary, therefore, the primary centres of
ossification for the metatarsals and phalanges are all
present (with the probable exception of the middle
phalanges of the lateral toes) by the end of the 5th
prenatal month.
 The normal sequence of appearance for the tarsal
bones is relatively constant and well documented.
 The calcaneus appears first, followed closely by the
talus and then the cuboid. The remainder of the tarsal
bones always appear after birth and the sequence
begins with the lateral cuneiform and is followed by
the medial and then the intermediate cuneiform, with
the navicular being the last to commence ossification.

 The foot is divided into the
 Hindfoot
 Calcaneus
 Talus
 Midfoot
 Cuboid
 Navicular
 Three cuneiforms
 Forefoot
 Metatarsals
 Phalanges
 The articulation between the hindfoot and the midfoot (midtarsal
joint) is frequently referred to as Chopart’s joint
 Named after surgeon who performed amputations at the
calcaneocuboid, talonavicular joint
 The articulation between the midfoot and the forefoot is
referred to as the Lisfranc joint
 Named after French surgeon Francois Chopart (1743–1795) who
performed amputations of the foot at this level
8

 There are three distinct groups or compartments of lower leg
musculature:
 posterior,
 lateral,
 and anterior.
 The posterior muscles are divided into superficial and deep
groups.
 The superficial group consists of gastrocnemius, soleus, and
plantaris.
 The gastrocnemius and soleus unite to form the Achilles tendon
that inserts into the tuberosity of the calcaneus.
10

 The Achilles tendon is not surrounded by a tendon sheath as are other
ankle tendons, but does have a peritenon covering.
 The fibers of achilles tendon are homogeneous and low signal on all MR
pulse sequences.
 On axial images the tendon has a flat or concave anterior surface.
Anterior to the tendon is a fat-containing space known as Kager’s fat pad.
 Between the distal Achilles tendon and the posterior calcaneal tuberosity
lies the retrocalcaneal bursa.
 The plantaris is a small muscle between the gastrocnemius and soleus;
this muscle is rudimentary and may be absent in 10% of the population.
Its long tendon runs along the medial border of the Achilles and inserts
into the calcaneus, the Achilles tendon itself, or the flexor retinaculum
13

 The deep group of posterior muscles consists
of the flexor hallucis longus, flexor digitorum
longus, and tibialis posterior.
 All three muscles arise from the posterior
tibia, fibula, and/or interosseous membrane.
 The tendons begin above the level of the
ankle and all three pass beneath the flexor
retinaculum.
14

 The anterior compartment contains the
tibialis anterior, extensor hallucis longus,
extensor digitorum longus, and peroneus
tertius muscles.
 The lateral compartment muscles include the
peroneus longus and brevis.
17

 Radiograph
 USG
 CT
 MRI
 A multimodality approach is often necessary for
complete radiologic assessment.
 Radiography, sonography, and computed tomography
all play important roles in the radiologic assessment
of the foot and ankle.
 However, magnetic resonance imaging (MRI) is often
the imaging modality of choice attributable to the
superior soft tissue contrast resolution, multiplanar
capability, lack of ionizing radiation, and ability to do
post contrast imaging.
18

 Plain radiographs are instrumental in the
initial evaluation of foot disorders.
 Weight-bearing views should be obtained
when possible.
 Dorsal-Plantar (DP) and Oblique - are
standard projections of the forefoot.
 Comparison views of the contralateral foot is
not routinely ordered but can be helpful in
difficult cases
19

 Sonography readily demonstrates the tendons
and peritendinous pathologies,
 Dynamic examination during flexion and
extension maneuvers
 Synovial pathologies can be evaluated
 Small amount of fluid along the posterior
tibial and common peroneal tendons in
normal subjects.
21

23
•No thickening
•Homogeneous
echogenicity
•No hypoechoic or
hyperechoic foci
•Nil neovascularisation

24
Neovascularization in the distal third
of tendon
Thickened – ‘Spindle Shape’
Abnormal Diagnosed by 1 or more of
the following findings
1.Tendon thickening with
heterogeneous echogenicity
2.Hypoechoic foci representing
intrasubstance tears (defined as linear
hypoechoic foci associated with
discontinuity of tendon fibres)
3.Calcifications and enthesiophytes at
the tendon attachment
4.Neovascularization

 CT has become an invaluable additional tool, particularly
for visualizing complex anatomic regions such as the
midfoot and for judging articular surface integrity.
 The foot and ankle are usually imaged with 2- to 3-mm
thick sections obtained in the axial plane (axial with
respect to the long axis of the body) with the patient
supine and the foot in neutral position.
 Imaging of only the affected extremity is recommended,
with the contralateral extremity removed from the scan
plane when possible, to minimize streak artifact and
optimize field of view and positioning for the area of
interest.
 When possible, direct coronal oblique sections are also
obtained. With the knee flexed and the foot flat on the
scan table, the gantry is tilted towards the knee as far as
possible to place the tibia nearly parallel with the plane of
section.
25

 Helical CT is useful in the trauma setting due
to difficulty positioning caused by pain,
splints and concomitant injuries.
 Helical 1-mm images are obtained in the
axial plane with 1:1 pitch, yielding
essentially isotropic images and high-quality
multiplanar reconstructions.
26

 Magnetic resonance (MR) imaging has opened
new horizons in the diagnosis and treatment
of many musculoskeletal diseases of the
foot.
 It demonstrates abnormalities in the bones
and soft tissues before they become evident
at other imaging modalities.
27

 Congenital variants and abnormalities
 Tendon abnormalities
 Impingement syndromes
 Infections
 Arthritis
28

 Accessory ossicles of the feet are
common developmental variants with almost 40
having been described. The more common ones
include:
 os peroneum
 os subfibulare
 os subtibiale
 os tibiale externum (accessory navicular)
 os trigonum
 os calcaneus secundaris
 os intermetatarseum
 os supratalare
 bipartite hallux sesamoid
 os supranaviculare
 Knowledge of their presence is helpful so that they
are not misdiagnosed as fractures.
30

 Secondary ossification centers are sometimes confused for
fractures.
 The os trigonum may be mistaken for the much less
common Shepherd fracture of the posterior process of
talus.
 Os trigonum syndrome is a mechanical tenosynovitis
caused by tethering of the flexor hallucis longus tendon by
the os trigonum.
 An os supranaviculare can simulate a navicular fracture.
31

 Accessory ossicles may be painful. CT features that have been
associated with pain include degenerative sclerosis and
irregularity, subchondral cyst-like changes and vacuum
phenomenon at the synchondrosis .
 A bipartite medial cuneiform is an uncommon variant that is
occasionally symptomatic and can be involved in trauma .
 The corticated nature of sesamoids in the forefoot distinguishes
them from acute fracture fragments and is usually readily
apparent on CT.
 Less noticed are the pathologic and potentially symptomatic
entities of these normal structures, including fracture,
osteonecrosis and degenerative change.
32

33
Os peroneum - “An os peroneum is
a small accessory bone located just
proximal to the base of the
5thmetatarsal and located within
the substance of peroneus
longus...”

34
Os tibiale externum
(accessory navicular) is a
large ossicle adjacent to
the medial side of the
navicular bone. The
tibialis posterior tendon
often inserts with a broad
attachment onto the
ossicle, which may cause
a painful tendinosis due
traction between the
ossicle and the navicular.

35
Os trigonum - “An os
trigonum is one of
the bony ossicles of the
foot and can be mistaken
for a fracture. it sits
posterior to talus on the
lateral foot radiograph.”

 Pes cavus
 Congenital talipes equinovarus (idiopathic
club-foot)
 Rocker bottom foot.
 Tarsal coalition
36

 Pes cavus refers to a descriptive term for a type
of foot deformity with an abnormally high
longitudinal arch of the foot (caved in foot).
 It can be associated with certain neuromuscular
disorders such as
 Charcot-Marie-Tooth disease : considered one of
the commonest associations in the western
world
 conditions that cause spastic paralysis
 spinal anomalies
 spinal dysraphisms
 spina bifida
37

 A lateral view is the key to assessment as the
dorso-plantar view can sometimes be normal
unless there an associated abnormality 2.
 On a lateral view there is:
 increase in the calcaneal inclination angle
 angle of the longitudinal arch greater than
170 degrees
 the mid-talar axis either extends above the
1st metatarsal or intersects the shaft distal
to its midpoint
 Hibb's angle less than 150 degrees.
38

 The calcaneal inclination
angle is drawn on
a weightbearing lateral foot
radiograph between
the calcaneal inclination
axis and the supporting
surface.
 It is a measurement that
reflects the height of the foot
framework, but is affected by
abnormal pronation or
supination of the foot:
 low: 10-20 degrees
 medium: 20-30 degrees
 high: 30+ degrees
39

 The angle of the
longitudinal arch is one
of the angles drawn on
the weightbearing
lateral foot radiograph.
The angle is formed
between the calcaneal
inclination axis and a
line drawn along the
inferior edge of the 5th
metatarsal.
 The normal angle is
150-170 degrees.
40

41
The mid-talar axis represents a line
drawn down the longitudinal axis of
the talus and can be drawn on
lateral and DP radiographs.
lateral view: line should bisect the
shaft of the first metatarsal
DP view: line should intersect (or
pass just medial to) the base of the
first metatarsal

 Hibb's angle is formed between the line
representing the long axes of the calcaneum
and the first metatarsal. The intersection of
the lines represents apex of the deformity.
 Normally Hibb's angle is greater than
150 degrees .
 Hibb's angle less than
150 degrees indicates pes cavus.
42

 It is a congenital deformity comprising four
elements:
(a) an equinus position of the heel;
(b) a varus position of the hindfoot;
(c) adduction and a varus deformity of the
forefoot;
(d) talonavicular subluxation.
 Before the ossification of the navicular
bone at 2 to 3 years of age, only the first
three elements can be verified
radiographically.
44

 Relatively common; the incidence is 1 or 2
/1000 births
 Boys are affected twice as often as girls.
 The condition is bilateral in one-third of
cases.
 Similar deformities are seen in neurological
disorders, e.g. myelomeningocele, and in
arthrogryposis.
 It’s mostly a problem passed from parents
to children (genetic), and it may run in
families.
45

 There can be an immense number (estimated at 200) of associations
which include:
 chromosomal anomalies
 18q deletion syndrome
 trisomy 18
 Wolf-Hirschhorn syndrome
 other syndromic conditions
 Freeman Sheldon syndrome
 Meckel Gruber syndrome
 Roberts syndrome
 renal anomalies
 prune belly syndrome
 renal agenesis
 connective tissue disorders
 Marfan syndrome
 Ehlers-Danlos syndrome
 spinal anomalies
 caudal regression syndrome
 diastematomyelia
 spina bifida
 skeletal dysplasias
 diastrophic dysplasia
46

 In the clubfoot deformity,
 the Kite anteroposterior talocalcaneal angle is
less than 20 degrees,
 the lateral angle is less than 35 degrees,
 and the TFM angle is greater than 15 degrees
 In the determination of the Kite
anteroposterior talocalcaneal angle, the lines
of the angle normally intersect the first and
fourth metatarsals; in the clubfoot anomaly,
these lines fall lateral to the normal points.
48

49
Lateral radiograph of the right foot shows
that the long axes of the talus and calcaneus
are nearly parallel. The longitudinal arch is
abnormally high. AP radiograph of the right
foot shows abnormally narrow talocalcaneal
angle, with severe adduction and supination
of the forefoot.

 It’s a rare neonatal condition usually affects
both feet.
 The foot is turned outwards (valgus) and the
medial arch is not only flat, it actually curves
the opposite way from the normal, producing
the appearance of a “rocker-bottom” foot.
 Passive correction is impossible
 The only effective treatment is by operation,
ideally before the age of 2 years.
51

 Associations
 aneuploidic syndromic
 trisomy 13
 trisomy 18
 18q deletion syndrome
 non aneuploidic non syndromic
 spina bifida
 arthrogryposis
52

 Radiographic features are characteristic:
 The calcaneum is in equinus and the talus points
into the sole of the foot, with the navicular
dislocated dorsally onto the neck of the talus.
54

 Tarsal coalition refers to the fusion of two or
more tarsal bones to form a single structure.
 This fusion may be complete or incomplete, and
the bridge may be fibrous (syndesmosis),
cartilaginous (synchondrosis), or osseous
(synostosis).
 Various bones may be affected, but most
commonly the coalition occurs between the
calcaneus and navicular bone.
 Pain, particularly associated with prolonged
walking or standing, is a typical presenting
symptom.
 On physical examination, peroneal muscular
spasm and restricted joint mobility (the so-
called peroneal spastic foot) are revealed.
55

 The vast majority (90%) of tarsal coalitions are
either:
 calcaneonavicular (~ 45%)
 usually involves the anterior process of the
calcaneus
 the anteater nose sign may sometimes be seen
 best seen on an oblique film
 talocalcaneal (~ 45%)
 usually involves the middle facet
 best seen on the lateral view
 C-sign - complete posterior ring around the talus
and sustentaculum tali
 talar beak sign due to impaired subtalar movement
 The remainder of the coalitions
(calcaneocuboid, talonavicular, cubonavicular)
are much less common .
56

57
The anteater nose sign refers to an anterior tubular prolongation of the
superior calcaneus which approaches or overlaps the navicular on a
lateral radiograph of the foot. This fancifully resembles the nose of an
anteater and is an indication of calcaneonavicular coalition .

60
A continuous C shaped arc is seen on lateral radiograph of ankle which is
formed by medial outline of dome of talus and posteroinferior aspect of
sustentaculum tali .

 The talar beak sign is seen in cases of tarsal
coalition, and refers to a superior projection
of the distal aspect of the talus. It is most
frequently encountered in talocalcaneal
coalition . It is thought to result from
abnormal biomechanic stresses at the
talonavicular joint.
61

62
(A) Harris view shows bulbous sustentaculum tali, with rounded inferior
contour and overgrowth in expected region of middle subtalar facet. (B) Lateral
radiograph shows dysmorphic sustentaculum tali, with bony overgrowth and
rounding of its inferior contour. Continuity of sustentaculum tali contour with that
of medial talus is the C-sign (C) Lateral radiograph shows talar beak arising at
talonavicular joint and curving away from joint and dysmorphic sustentaculum tali
and C-sign (D) Lateral radiograph shows rounded lateral process of talus and
dysmorphic sustentaculum tali Bony prominence at dorsal margin of talar head has
features of both osteophyte and beak, perhaps because this is an older patient who
has developed osteoarthritis

 Achilles tendon: occur in atheletes esp
runners.
 Tibialis posterior: in middle age obese
women
 Peroneal tendons: pateints with previous
lateral ankle sprains
 Other tendons are rarely injured.
63

 Tendinosis(collagen degeneration and vascular
ingrowth)
 Paratendinosis(inflamation of the paratenon)
 Tenosynovitis(inflamation of the tendon sheath)
 Partial tear
 Complete tear( tendon rupture)
 Tendon dislocation and entrapment
 These conditions often coexist, and overlap in their clinical,gross,
and histologic manifestations can make them indistinguishable at MR
imaging
64

 The MR imaging characteristics of tendinosis
include
 a fusiform shape
 focal areas of increased tendon girth
 associated with increased signal intensity within
the tendon on T1-weighted and protondensity–
weighted images.
 T2 signal intensity alterations are noted when
significant intrasubstance degeneration is
present.
65

Tendonosis-Neovascularisation
66

 Caused by inflammation or mechanical irritation
of the tendon sheath and peritenon,
respectively.
 MR images reveal fluid accumulation, synovial
proliferation, or scarring within the tendon
sheath or adjacent soft tissues.
 Stenosing tenosynovitis occurs when synovial
proliferation and fibrosis surround the tendon,
causing entrapment and even rupture.
 It manifests as areas of intermediate to low
signal intensity in the soft tissues around the
tendon with all MR imaging sequences.
68

69
fluid is noted within the tendon sheath of the tibialis posterior tendon. The
tendon itself is of normal echotexture with no evidence of tendinopathy.
Tenosynovitis

Peritendinitis & chronic tendinosis TA
Peritendinitis & chronic tendinosis TA
74

 MRI Findings:
 Partial rupture manifests on T1-weighted and
proton-density–weighted images and occasionally
 on T2-weighted images as an area within the
substance of the tendon having a signal intensity
similar to that seen in advanced tendinosis.
77

 Achilles tendon injuries may be classified as
noninsertional or insertional.
 The former group includes diffuse acute and
chronic peritendinosis, tendinosis, and a
rupture 2–6 cm above the insertion of the
tendon on the calcaneus.
 The latter group includes insertional Achilles
tendinosis, which may be associated with
Haglund deformity of the calcaneus.
80

 Weinstabi et al classified Achilles tendon
lesions into four types on the basis of MR
imaging findings.
 Type I represents inflammatory reaction;
 Type II, degenerative changes;
 Type III, partial rupture;
 Type IV, complete rupture.
81

 A patient with isolated paratendinitis
demonstrates a normal intratendinous
structure,
 whereas peritendinous effusion,
 irregularities of tendon margins and
 adhesions related to scarring of the
paratenon,
 heterogeneous appearance of the pre-
Achilles tendon fat pad, are the main
findings
82

 Achilles tendinosis is demonstrated as
 tendon swelling, which is often bilateral, and
textural heterogeneity with intratendinous
focal hypoechoic areas
 US can reveal subtle changes in the fibrillar
pattern, including thickening, fragmentation
and disappearance of specular echoes
84

 Achilles peritendinosis manifests at MR
imaging as linear or irregular areas of altered
signal intensity in the pre–Achilles tendon fat
pad, a finding that indicates the presence of
edema or scarring of the peritenon. The
tendon itself is normal.
 Achilles tendinosis manifests on axial MR
images as loss of the anterior concave or flat
surface of the Achilles tendon and on sagittal
images as fusiform thickening of the tendon.
 Areas of increased signal intensity within the
tendon are also noted.
85

 At MR imaging, partial Achilles tendon tears
demonstrate heterogeneous signal intensity and
thickening of the tendon without complete
interruption.
 Differentiation between partial tear and severe
chronic Achilles tendinosis may be difficult apart
from clinical history.
 Acute partial tears are often associated with
subcutaneous edema, hemorrhage within the
Kager fat pad, and intratendinous hemorrhage at
MR imaging, whereas chronic tendinosis does not
usually demonstrate increased subcutaneous or
intratendinous signal intensity on T2-weighted
images.
87

 Complete Achilles tendon rupture manifests
as discontinuity with fraying and retraction
of the torn edges of the tendon.
 In acute rupture, the tendon gap
demonstrates intermediate signal intensity
on T1-weighted images and high signal
intensity on T2-weighted images, findings
that are consistent with edema and
hemorrhage,
 In chronic ruptures, scar or fat may replace
the tendon
88

 Haglund's deformity represents insertional
tendinitis with a posterosuperior calcaneal
bony prominence and retrocalcaneal tendo
Achilles bursitis
90

94Chronic partial rupture with extensve scar formation and bursitis

 The Haglund syndrome refers to the triad of
 insertional achilles tendinopathy
 retrocalcaneal bursitis and
 and retro tendo-achilles bursitis
 This results in pain at the back of the heel.
 It is associated with calcaneal spurs, and the
wearing of high heels (thus the colloquial
term "pump-bump") or stiff backed shoes in
general.
95

 The Achilles tendon is the tendon most frequently involved in
metabolic disorders
 In gout, deposition of urate tophi may result in intratendinous
nodules or diffuse thickening of the tendon,
 Heterozygous familial hypercholesterolemia, an inherited
disorder leading to premature atherosclerosis,
 US can depict striking bilateral tendon swelling and a high-grade
textural heterogeneity and disappearance of the fibrillar pattern
with focal or diffuse hypoechoic areas, the intratendinous
xanthomas, before these become clinically apparent
 On MR Fusiform thickening of the Achilles tendon associated with
intrasubstance heterogeneity and stippling are consistent with
the presence of xanthoma.
97

Xanthoma of the Achilles tendon in a patient with
familial hypercholesterolemia
98

 Acute or chronic dysfunction of the posterior
tibial tendon encompasses a spectrum of
abnormalities ranging from tenosynovitis and
tendinosis to partial or complete rupture of
the tendon.
 Acute tenosynovitis is related to overuse and
is usually encountered in young, athletic
individuals. At MR imaging, fluid is seen
within the tendon sheath
100

 Chronic posterior tibial tendon rupture
typically develops in women during the 5th
and 6th decades of life and is associated with
progressive flat foot deformity.
 The tear is commonly noted behind the
medial malleolus, where the tendon is
subjected to a significant amount of friction.
 Acute partial or complete rupture of the
posterior tibial tendon in young, athletic
individuals is less common and is usually seen
at the insertion of the tendon on the
navicular bone.
101

 MR imaging classification of chronic posterior
tibial tendon ruptures divides these injuries into
three types.
 Type I partial tear consists of an incomplete tear
with fusiform enlargement, intra-substance
degeneration, and longitudinal splits
 Type II partial tear of the posterior tibial tendon.
On axial images, a decrease in the diameter of
the tendon, usually without signal intensity
alterations. The caliber of the tendon may be
equal to or less than that of the adjacent flexor
digitorum longus tendon
 Type III posterior tibial tendon tears there is
complete disruption of the tendon fibers
102

 Osteoarthritis
 Crystal artropathy(gout)
 Rheumatoid arthritis
 Seronegative arthropathies
 Septic arthritis
 Charcot arthropathy(neuroarthropathy)
104

 Trauma is the most common predisposing factor,
including injuries such as lateral ligament tear
with resultant instability and/or osteochondral
injury, as well as intraarticular
fracture,Degenerative arthropathy, or
osteoarthritis, commonly affects the ankle.
 Classic signs include joint space
narrowing,marginal osteophytes, intraarticular
body formation, subchondral cysts, and
subchondral sclerosis.
 Osteoarthritis is also quite common at the
midfoot, typically resulting in dorsal spurring at
multiple articulations (also called “dorsal
proliferative change”).
105

 Gout is a metabolic disorder characterized by
recurrent episodes of arthritis associated with the
presence of monosodium urate monohydrate crystals
in the synovial fluid leukocytes and, in many cases,
gross deposits of sodium urate (tophi) in periarticular
soft tissues.
 Serum uric acid concentrations are elevated.
 The great toe is the most common site of
involvement in gouty arthritis;
 the condition known as podagra, which involves the
first metatarsophalangeal joint, occurs in
approximately 75% of patients.
 Other frequently affected sites include the ankle,
knee, elbow, and wrist.
 Most patients are men, but gouty arthritis is seen in
postmenopausal women as well.
107

 Erosions, which are usually sharply marginated, are initially
periarticular in location and are later seen to extend into the
joint
 an “overhanging edge” of erosion is a frequent identifying
feature
 Intraosseous defects are present secondary to formation of
intraosseous tophi .
 Lack of osteoporosis, helps differentiate this condition from
rheumatoid arthritis.
 If erosion involves the articular end of the bone and extends into
the joint, part of the joint is usually preserved.
 In chronic tophaceous gout, sodium urate deposits in and around
the joint are seen, creating a dense mass in the soft tissues
called a tophus, which frequently exhibits calcifications
 Characteristically, tophi are randomly distributed and are usually
asymmetric; if they occur in the hands or feet, they are more
often seen on the dorsal aspect
108

 In the foot, rheumatoid arthritis has a predilection
for the metatarsophalangeal joints, especially the
fifth.
 Periarticular osteopenia is variably present.
 Although the intertarsal, subtalar, and ankle joints
may be involved.
 Involvement at the ankle can create a characteristic
erosion of the synovial recess at the distal tibiofibular
joint.
 Joint destruction and capsular distension can result in
deformities including subluxation/ dislocation
 Chronic inflammatory tenosynovitis can result in
tendon tear and dysfunction, causing additional
deformity; posterior tibial tendon dysfunction is
particularly common.
110

 seronegative arthropathy and enthesopathy, where
erosions and bone proliferation occurs.
 In the foot, this typically affects the metatarsophalangeal
and interphalangeal joints.
 Interphalangeal erosions may result in the pathognomonic
“pencil-in-cup” appearance.
 Acro-osteolysis can occur along with nail involvement.
 Proliferative bone formation manifests as periostitis and in
areas
of bone erosion fluffy bone production occurs.
 Occasionally, if severe, erosions may result in ankylosis or
joint destruction (arthritis mutilans).
 Enthesial involvement resulting in erosions or “fuzzy spurs”
may occur at the plantar fascia or other tendon, ligament,
or fascial attachment sites.
 Bursitis may also occur with focal soft-tissue swelling.
113

 Septic arthritis of the foot and ankle, like
any other region,may occur secondary to
penetrating trauma/direct implantation,
postoperatively, due to contiguous spread, or
hematogenous spread.
 The imaging features consist of a joint
effusion, with loss of the sharp cortical
margins of the subarticular bone.
 Joint space loss is rapid in acute septic
arthritis, and marginal erosions may develop
mimicking an inflammatory arthropathy
116

 Osteomyelitis of the foot and ankle is usually
seen in susceptible populations, particularly
diabetic or paralyzed patients.
 In these patients, contiguous spread is by far
the most common mode of infection, arising
via skin ulceration.
117

 Neuropathic osteoarthropathy is an arthritic
process that is often aggressive, resulting from
repetitive micro- and macrotrauma that heals
ineffectively due to ischemia and reduced
nociception.
 Disease may be seen in various neurological
conditions involving the foot/ ankle such as
leprosy, common in diabetics with peripheral
neuropathy.
 In diabetic population, the Lisfranc joint and
intertarsal joints are most commonly involved,
followed by the Chopart joint, subtalar and
tibiotalar joint, and the metatarsophalangeal
joints.
119

 Radiographically in the early stage diffuse soft tissue
swelling and occasionally mild offset of a joint.
 The disease progress rapidly, with erosions and even
frank joint destruction.
 Often in the late stage there is excessive bone
production (sclerosis and spurring), and subchondral
cystic change which in addition to deformity leads to
the classic appearance of chronic neuropathic
osteoarthropathy.
 Articular surfaces degenerate over time and may
fragment, becoming distorted, incongruent, and
generally disorganized, with debris and body
formation.
 Neuropathic osteoarthropathy has been characterized
radiographically as dislocation, debris,
disorganization, deformity, and increased density.
120

 MR imaging has been shown to be highly sensitive in the
detection and staging of a number of musculoskeletal
infections including cellulitis, soft-tissue abscesses, and
osteomyelitis.
 MR imaging has greater specificity and better spatial
resolution than bone scintigraphy and also has the capacity
to provide a quicker diagnosis.
 Differentiation between neuroarthropathy and infection
may be difficult with any imaging technique.
 At MR imaging, neuroarthropathy exhibits characteristic
findings including bone fragmentation, dislocations,
cortical and periosteal thickening, joint effusion, and soft-
tissue swelling. In most cases, the bone marrow appears
hypointense on both T1- and T2-weighted images.
 In osteomyelitis, on the other hand, the bone marrow
appears hypointense on T1- weighted images and
hyperintense on T2-weighted images.
122

 The most common compressive neuropathies
of the ankle and foot are tarsal tunnel
syndrome and Morton neuroma
123

 Tarsal tunnel syndrome is characterized by
pain and paresthesia in the plantar aspect of
the foot and toes.
 This syndrome is most frequently unilateral,
as opposed to carpal tunnel syndrome, which
is typically bilateral.
 Nerve entrapment or compression can occur
at the level of the posterior tibial nerve or
its branches producing different symptoms
depending on the site of compression
124

 Intrinsic and extrinsic causes of posterior tibial nerve
compression have been identified.
 Intrinsic lesions that often produce tarsal tunnel syndrome
include
 Accessory muscles,
 Ganglion cysts,
 Neurogenic tumors,
 Varicose veins,
 lipomas,
 synovial hypertrophy, and scar tissue.
 Extrinsic causes
 Foot deformities,
 Hypertrophic and accessory muscles,
 accessory ossicle (os trigonum), and excessive pronation
 In about 50% of cases, the cause of tarsal tunnel syndrome cannot
be identified.
 Relief of symptoms following retinacular release is frequently
seen in these idiopathic cases.
125

 Morton neuroma (interdigital neuroma) is
actually a fibrosing degenerative process
produced by compression of a plantar digital
nerve.
 The condition has a female predilection and is
frequently seen between the heads of the third
and fourth metatarsals, although all web spaces
may be involved.
 The nerve becomes thickened, and associated
bursitis is often present.
 Exquisite tenderness is elicited on lateral
compression of the metatarsals.
 The pain can radiate to the toes and may be
accompanied by numbness
127

 MR imaging has proved highly accurate in the
diagnosis of Morton neuroma,
 manifests as a dumbbell shaped mass located
between the metatarsal heads and having
intermediate to low signal intensity on both
T1- and T2-weighted images.
 T1- weighted sequences are probably more
helpful because the hypointense neuroma is
made more conspicuous by the surrounding
hyperintense fat.
 The low signal intensity of Morton neuroma is
attributed to the presence of fibrous tissue.
128

Transverse view: Hypoechoic focus between 3rd and 4th interspace.

 Osteonecrosis of the ankle and foot typically occurs in the
talus as a consequence of talar neck fractures with
vascular compromise of the bone at the level of the sinus
tarsi.
 Osteonecrosis of the tarsal navicular bone can occur in
children (Kohler disease)
 Manifests radiographically as sclerosis, irregularity, and
fragmentation of the bone.
 A form of osteonecrosis of the tarsal navicular bone has
also been described in adults (Mueller-Weiss syndrome).
 Osteonecrosis of the ankle and foot region is also
frequently seen in the second metatarsal head (Freiberg
disease), with sclerosis and flattening of the metatarsal
head seen at conventional radiography, and in the first
metatarsal sesamoid bone
133

135
Freiberg disease. (A) T2 image shows extensive bone marrow edema and
subchondral impaction (arrow) and effusion suggesting more acute changes. (B)
Proton density images show subchondral fracture with impaction of cortex and
subchondral bone plate (arrow). (C) Axial, (D) sagittal images of late-stage Freiberg
disease with secondary osteoarthritis and subchondral cyst (arrow). Collapsed
subchondral bone with a low-grade stress response.

 Pigmented villonodular synovitis (PVNS) is
characterized by inflammatory proliferation of
the synovium associated with deposits of
hemosiderin.
 It can be present in any joint, tendon sheath, or
bursa but is most frequently seen in the knee,
hip, ankle, and elbow.
 When it originates in the tendon sheaths, the
term giant cell tumor of the tendon sheaths is
often used.
 In the foot, this lesion predominantly involves
the peroneal and flexor tendon sheaths
136

 PVNS can occur at age 20–50 years and may
manifest as a focal mass or as a generalized
lesion involving the entire joint space.
 Pressure erosions may be present in the diffuse
form.
 These lesions manifest clinically as joint pain
and swelling of long duration, and most are
slowly progressive.
 At pathologic analysis, PVNS is characterized by
synovial inflammation with giant cell
proliferation, collagen, and lipid-laden
macrophages.
 Treatment of PVNS often consists of resection of
the lesion.
137

 characteristic MR
imaging features due
to the paramagnetic
effect of
hemosiderin, which
produces focal areas
of hypointensity with
all pulse sequences,
 mixed with
hypointense areas on
T1-weighted images
and hyperintense
areas on T2-weighted
images.
138

 Plantar fasciitis is a painful condition caused by
repetitive injury to the proximal plantar fascia,
at or near its origin from the calcaneus.
 Individuals with pes planus and overpronation
are predisposed.
 Although spur formation at the inferior calcaneus
is often implicated in this process, it actually has
little association with pain;
 Although plantar fascial thickening may be
suggested on the lateral radiograph, this finding
is not necessarily related to acute, symptomatic
fasciitis
142

 MR imaging is useful in distinguishing plantar fasciitis from
other causes of heel pain and in excluding plantar fascia
tears.
 On sagittal and coronal MR images, the normal plantar
fascia appears as a thin, hypointense structure extending
anteriorly from the calcaneal tuberosity.
 The plantar fascia has a normal thickness of 3.22 mm ±
0.53 and flares slightly at the calcaneal insertion.
 When inflammatory changes take place, it becomes
thickened (up to 7–8 mm) and demonstrates intermediate
signal intensity on T1-weighted and proton-density–
weighted images and hyperintensity on T2- weighted
images .
 These changes are most prominent in the proximal portion
of the plantar fascia at or near its insertion on the
calcaneus.
 Signal intensity changes may also be present in the
subcutaneous fat, in the deep soft tissues, and in the
calcaneus near the fascial insertion.
144

 The sinus tarsi is a lateral space located between the talus and the
calcaneus.
 It contains the cervical and interosseous talocalcaneal ligaments, the
medial roots of the inferior extensor retinaculum, neurovascular
structures, and fat.
 Sinus tarsi syndrome is caused by hemorrhage or inflammation of the
synovial recesses of the sinus tarsi with or without tears of the associated
ligaments.
 This disease entity commonly occurs following an inversion injury and is
often associated with tears of the lateral collateral ligaments.
 It may also be related to rheumatologic disorders and abnormal
biomechanics such as flat foot deformity secondary to posterior tibial
tendon tear.
 Patients with sinus tarsi syndrome present with hindfoot instability and
pain along the lateral aspect of the foot.
 The MR imaging characteristics of sinus tarsi syndrome include the
obliteration of fat in the sinus tarsi space. The space itself is replaced by
either fluid or scar tissue, and the ligaments may be disrupted.
 Osteoarthritis of the subtalar joint and subchondral cysts may be present
in advanced cases.
145

 Sinus tarsi syndrome (STS) is a clinical finding that
mainly consists of pain and tenderness of the lateral
side of the hindfoot, between the ankle and the
heel.
Aetiology
 STS probably occurs following one single or a series
of ankle sprains that also result in significant
injuries to the talocrural interosseous and cervical
ligaments.
 This causes instability of the subtalar joint in
supination and pronation movements.
 In summary, STS can be primarily described as an
instability of the subtalar joint due to ligamentous
injuries that result in synovitis and scar tissue
formation in the sinus tarsi. Haemorrhage or
inflammation of the synovial recesses of the sinus
tarsi can also cause scarring without tears of the
associated ligaments.
146

Plain film
 Osteoarthritis of the subtalar joint and intraosseous
cysts may be present in advanced cases.
CT
 Shows secondary bony changes earlier than plain
films.
Bone scan - scintigraphy
 Inflammatory changes may be attributed to the
sinus tarsi / subtalar region.
MRI
 Probably the best test to show changes in the
tissues of the sinus tarsi including inflammation,
scar tissue formation or ligamentous injuries.The
T1-hyperintense fat in the sinus tarsi space is
replaced by either fluid or scar tissue, and the
ligaments may be disrupted. Ganglion cysts in the
region of the sinus tarsi may compress the posterior
tibial nerve.
147

149
Diffuse fluid signal or oedema around the interosseous ligaments in the
sinus tarsi.

 The initial evaluation should always
commence with plain radiographic
assessment.
 MR imaging is the modality of choice for
optimal detection of most soft-tissue
disorders of the tendons,ligaments, and
other soft-tissue structures of the ankle and
foot.
150

Imaging of foot in non trauma and non neoplastic diseases

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