This document provides an overview of various conditions involving the foot and ankle that can be evaluated on radiology imaging. It discusses accessory ossicles that can occur in the foot and be a cause of pain. It also reviews conditions like rocker bottom foot, tarsal coalition, fractures around the ankle joint involving the lateral malleolus, tibial plafond, talus and calcaneus. Other topics covered include osteochondral defects of the talus, accessory ossicles of the foot, and angles used to evaluate calcaneal fractures.

1. Dr. Manmohan Bir Shrestha
FOR RADIOLOGY

2. Contents
 Accessory ossicles of the foot
 Rocker bottom foot
 Tarsal coalition
 Fractures around the ankle
 Plantar fascia
 Brodie’s abscess in distal tibia
 Soft tissue masses around ankle
 Retrocalcaneal bursitis
 Haglund syndrome
 Achilles tendinopathy
 Achilles tendon tears

3. Accessory ossicles of the foot
 are secondary ossification centers that are separate from
the adjacent bone
 Usually round or ovoid
 have well defined smooth cortical margins on all sides.
 Clinical importance
 May fracture
 Can cause pain
 May be involved in rheumatoid arthritis, osteoarthritis, infections
& hyperparathyroidism

4. Accessory ossicles of the foot
 Os tibiale externum
 Os trigonum
 Os peroneum
 Os vesalianum
 Os subtibiale
 Os subfibulare
 Os supratalare
 Os cancaneus secundarius

5. Os tibiale externum
 Also called accessory navicular
 is present adjacent to the medial side of navicular
 Can cause painful tendinosis of tibialis posterior
tendon
 Imaging
 best visualized on the lateral-oblique view
 may appear as a 'hot spot' on bone scan
 on MRI, bone marrow oedema can be seen

6. Bilateral Os tibiale externum

7. Bilateral Os tibiale externum

8. Os peroneum
 Commonly found – 8%
 located at the lateral plantar aspect of the cuboid
within the substance of the peroneus longus tendon
 D/D
 Os vesalianum
 Apophysis of the 5th metatarsal
 Avulsion fracture

9. Os peroneum

10. Os peroneum

11. Fractured Os peroneum

12. Os vesalianum
 situated at the base of the fifth metatarsal in the
peroneus brevis tendon
 Less common than os peroneum
 D/D
 Os peroneum
 Apophysis of 5th metatarsal – in children
 Avulsion fracture

13. Os vesalianum

14. Os trigonum
 sits posterior to the talus on the lateral foot radiograph
 Incidence – about 7% of population

15. Less common accessory ossicles
 Os subtibiale
 related to the posterior colliculus of the medial malleolus
 Os subfibulare
 lies at the tip of the lateral malleolus
 Os supratalare
 located at the superior aspect of the talar head or neck
 Os cancaneus secundarius
 Located at anterior calcaneal process

16. Rocker bottom foot

17. Rocker bottom foot/ congenital vertical talus
 Congenital anomaly
 Characterized by prominent heel/ calcaneus & a convex
rounded sole
 results from dorsal and lateral dislocation of the
talonavicular joint.
 Foot resembles bottom of a rocking chair
 In adult, it can occur secondary to
 Neuromuscular disorder
 Diabetic foot (charcot joint)

18. Imaging findings
 fixed equinus: plantarflexion of the calcaneus
 vertical talus: plantarflexion of the talus
 irreducible dorsal subluxation or dislocation of the
navicular
 forefoot valgus: divergence of bases of the metatarsal heads
on AP and superimposition of the metatarsal bones on the
lateral view
 long axis of the talus passes plantar to metatarsal axis on
lateral view and medial to the first metatarsal on AP view

19. Rocker bottom foot
AP view shows calcaneus valgus
& metatarsal valgus. The long
axis of talus is much medial to
st
On lateral view, there is equinus of the
calcaneus and vertical orientation of talus.
Navicular has not yet ossified

20. Tarsal coalition

21. Tarsal coalition
 complete or partial union between two or more bones
in the midfoot & hindfoot
 Incidence – about 5 % of population
 Patient usually present in adolescence
 refers to developmental fusion rather than fusion that
is acquired secondary to conditions such
as rheumatoid arthritis, trauma or post-surgical.

22. Types
 They may be of 3 types, depending on the tissue which
bridges between the two bones. The three types are 1:
I. bony: synostosis
II. cartilaginous: synchondrosis
III. fibrous: syndesmosis

23. Tarsal coalition
 Calcaneonavicular – about 45%
 Talocalcaneal - about 45%
 Less common are
 Calcaneocuboid
 Talonavicular
 cubonavicular

24. Calcaneonavicular coalition
 Oblique view x-ray is best
 MRI - more helpful in assessing and characterising
cartilaginous and fibrous coalition

25. Calcaneonavicular coalition

26. Talocalcaneal coalition
 Although all three facets of the talocalcaneal joint can be
involved, the middle facet is most commonly involved.
 Often requires cross-sectional imaging for accurate diagnosis
 Plain radiograph
 C-sign(lateral film) – posterior continuity of talus & sustentaculum
tali
 Talar beak sign (latearal film) – prominent beak at the anterior end
of talus
 non-visualisation of the middle articular facet
 Sclerosis around the articular margins of the talocalcaneal joint
 CT – coronal reformats are best
 MRI

27. C sign in Talocalcaneal coalition
Red: talus; blue: sustentaculum tali - blue line is continuous between the talus
and sustentaculum tali demonstrating coalition.

28. A case of Talocalcaneal coalition

29. Fractures around the ankle
 Lateral malleolus fracture
 Fracture through the Tibial plafond
 Talus fracture
 Calcaneus fracture

30. Lateral malleolus fracture
 commonly the result of twisting injury of the talus in
ankle mortise.
 Radiographs are usually sufficient for the management
of what are typically simple fractures.
 CT axial images through both ankles are useful when
the integrity of the syndesmosis is questioned.
 “Weber” staging system for ankle fractures – to
understand mechanism of syndesmotic injury.
 syndesmotic injuries usually require screw fixation

31. Weber classification of lateral malleolar fractures
 Type A
 Below talar dome
 Usually transverse
 Syndesmosis intact
 Deltoid ligament intact
 Type B
 distal extent at the level of the talar dome
 Usually spiral
 syndesmosis usually intact, but widening of the distal tibiofibular joint
(especially on stressed views) indicates syndesmotic injury
 deltoid ligament may be torn, indicated by widening of the space between
the medial malleolus and talar dome
 Type C
 above the level of the ankle joint
 tibiofibular syndesmosis disruption with widening of the distal tibiofibular
articulation
 medial malleolus fracture or deltoid ligament injury often present

32. Weber classification of lateral malleolar fractures

33. Weber classification of lateral malleolar fractures

34. Weber A
Transverse fracture through lateral malleolus below ankle joint – “Weber A”

35. Weber B
There is oblique fracture of distal fibula.
fracture extends distally to the level of the ankle joint.
There is no significant widening of the tibiofibular joint to suggest syndesmosis tear.

36. Weber C
Widened
syndesmosis

37. Fracture through the Tibial plafond

38. Fracture through the Tibial plafond
 In adult –
 Pilon fracture
 In adolescents
 Tillaux fracture
 Triplane fracture

39. Pilon Fracture
 any tibial fracture that involves the distal articular
plafond and are typically the result of an axial loading
force
 can produce significant comminution with multiple
displaced fracture fragments
 X-ray & CT
 fractures lines are seen extending into the tibiotalar
articular surface


40. Pilon fracture
28 yrs. after Road
Traffic Accident
There is a comminuted
distal tibial fracture
extending into
the tibial plafond

41. Juvenile Tillaux fracture
 Salter-Harris type 3 fracture
 Have characteristic appearance on CT
 Mechanism - an external rotation force pulling on the
anterior tibiofibular ligament, causing avulsion of the
anterolateral corner of the distal tibial epiphysis with
variable amount of displacement
 Why always laterally?
 because the distal tibial physis fuses from medial to lateral as
a child matures
 Age
 Adolescents in whom, lateral growth plate has not fused
12-15 years

42. Tillaux fracture – 15 years male
Tillaux fracture, i.e. Salter-Harris III fracture of anterolateral
aspect of distal tibial epiphysis, minimally displaced.

43. Triplane fracture
 Salter-Harris type 4
 Multiplanar CT scans are ideally suited to visualize
these fractures in all planes
 The name is due to the fact of the fracture
expanding both in frontal and lateral as well as
transverse planes
 It comprises of
 a vertical fracture through the epiphysis
 a horizontal fracture through the physis
 an oblique fracture through the metaphysis
 Age
 adolescents

44. Triplane fracture in adolescent
Tibial physis closed medially. Fracture in lateral tibia extending into epiphysis
and metaphysis consistent with Triplane fracture. No major dislocations.

45. Review of Salter-Harris classification of
physeal fractures
 1 – Slipped
 2 – Above
 3 – Lower
 4 – Together
 (epi, metaphysis &
growth plate)
 5 - Rammed

46. Talar Fracture

47. Talar fracture
 Location
 Head
 Neck
 Body
 Talar dome osteochondral fracture
 Posterior talar process fracture
 Lateral talar process fracture

48. Talar dome osteochondral defect/injury
 These are are focal areas of articular damage with
cartilage damage and injury of the adjacent
subchondral bone
 Plain x-ray findings can be normal in early stages
 MRI more sensitive and specific

49. Anderson staging of osteochondral
defect
 Stage I
 “subchondral trabecular compression”
 Plain film & CT negative
 Bone marrow edema in MRI
 Stage II
 “incomplete separation of the fragment,”
 X-ray – only thin sclerotic rim
 IIa – if subchondral cyst
 Stage III
 “unattached, undisplaced fragment,”
 Presence of synovial fluid in T2 around fragment
 Stage IV
 Displaced fragment

50. Anderson Stage I defect

51. Anderson Stage II defect

52. Anderson Stage IIa defect

53. Anderson Stage III defect

54. Anderson Stage IV defect

55. Frequently missed in plain films

56. Bohler/Tuber/Calcaneal angle
 Angle between 2 lines in
lateral film
 Line 1 – vertex to
postero-superior edge
 Line 2 – vertex to
anterior horn of
calcaneum
 Normal
 20-40
 Less than 20 degrees in
calcaneal fracture

57. Gissane/critical angle
 In lateral film, formed by
downward & upward
slopes of calcaneal
superior surface
 Normal
 120-145
 Increased in calcaneal
fracture

58. Chopart fracture/injury
 Fracture/dislocation of the mid-
tarsal joint i.e. talonavicular &
calcaneocuboid joints, which
separates hindfoot from midfoot
 The commonly fractured bones are
calcaneum, cuboid & navicular
 The foot is usually dislocated
medially & superiorly as it is
plantar flexed & inverted, usually
as a result of high energy impact
 Where the foot is everted, lateral
displacement occurs

59. Lisfranc injury/fracture
 are the most common type of
dislocation involving
the foot and correspond to the
dislocation of the articulation of
the tarsus with the metatarsal
bases
 Displacement can also occur
from fractures at distal
metatarsals

60. A case of Lisfranc fracture/dislocation
Figure - Divergent Lisfranc dislocation in a 34-year-old who was the front passenger in
a motor vehicle accident. Radiographs were obtained in the emergency department.
Anteroposterior (A) and oblique (B) views of the foot reveal lateral dislocation of the
second through fifth metatarsals. The white arrow points to a fragment fractured off
the base of the second metatarsal.
Less obvious on the lateral view

61. Plantar fascia
Plantar fasciitis
Plantar fascia tear
Plantar fascia calcification

62. Plantar fascia
 dense collection of collagen fibres on the sole (plantar
surface) of the foot. These fibres are mostly longitudinal
but also transverse
 Attachments
 Posteriorly it attaches to the medial process of the tuberosity
of the calcaneus, proximal to flexor digitorum brevis. It is
narrow and thick at this attachment and becomes more broad
and thin distally and anteriorly.
 Anteriorly it divides into five heads, one for each toe, just
proximal to the heads of the metatarsals. The superficial
layers of these fibres insert into the dermis at the ball of the
foot and the crease between the ball and the toes via the
retinacula cutis (skin ligaments). The deep layers of each digit
become septa that separate the digital flexor tendons from
the lumbricals and the digital vessels and nerves.
 Laterally it covers abductor digiti minimi.
 Medially it covers abductor hallucis and merges with
the flexor retinaculum and dorsalis paedis fascia.

64. X-RAY
MRI
HYPOINTENSE

65. Plantar fascitis
 Most common cause of pain in heel
 is a stress reaction occurring at the origin of the
plantar aponeurosis from the calcaneus, typically at
the medial calcaneal tubercle.
 Etiology - degenerative changes from repetitive
microtrauma in the origin of the plantar fascia cause
traction periostitis and microtears

66. Imaging Plantar Fascitis
 Plain radiograph
 Non-specific
 Associated calcaneal spur can be found
 MRI
 Thickened >4.5 mm
 Edema around the origin of the aponeurosis
 there may be edema in the underlying calcaneal
bone marrow

67. A case of plantar fasciitis –
Thick fascia near origin with high signal intensity

68. Plantar fascial tear
 refer to disruption of plantar fascial fibres which
can occur in associated with longstanding plantar
fascitis or those treated with steroid injections.
 The tears can be complete (i.e. rupture) or
incomplete.
 MRI – T1WI
 absence of T1-weighted low signal intensity at the site
of complete rupture or partial loss of T1-weighted low
signal intensity.


69. Plantar fascia calcification

70. Brodie’s abscess in distal tibia
 chronic intraosseous abscess resulting from
incomplete resolution of acute osteomyelitis
 Distal tibial metaphysis – 1 of the common location of
brodie’s abscess.
 Rarely cross the growth plate & epiphysis in children
 Age- children with unfused epiphyseal plates
 Pathology – Staphylococcus aureus

71. Imaging
 Plain radiograph
 lytic lesion often oval that is oriented along the long axis of
the bone
 surrounded by a thick dense rim of reactive sclerosis
 Periosteal reaction - +-
 CT
 central intramedullary hypodense cystic lesion with thick rim
ossification
 Extensive periosteal reaction and bone sclerosis around the
lesion
 MRI
 T2 & STIR hyperintense rim with surrounding hypointense
sclerotic rim
 Adjacent bone marrow edema +-

72. Case of 13 yrs. Old with Brodie’s abscess in distal tibia
Lytic lesion in
metadiaphyseal
region of distal tibia
MRI
Bilobed T1 hypointense and T2 hyperintense lesion
with surrounding sclerosis.
Adjacent marrow edema is also present

73. Soft tissue masses/tumors around Ankle
I. Synovial cysts or ganglia
II. Schwannomas
III. Plantar fibromas
IV. Giant cell tumor of the tendon sheath

74. Synovial cysts or ganglia
 Most common around ankle & foot
 are para-articular fluid-filled sacs or pouch-
like structures containing synovial fluid and lined by
synovial membrane
 MRI – uniformly bright on fluid-sensitive images

75. Synovial cyst in 51 year old
Lateral radiograph shows a
round soft tissue mass
dorsal to the metatarsals
T1 – Iso
T2 – Bright
Post contrast – peripheral
enhancement

76. Plantar fibromas
 Plantar fibromas can have variable signal
characteristics but are typically dark on all sequences
 These are usually found in the plantar fat adjacent to
the aponeurosis, usually close to the calcaneus

77. A case of Plantar fibroma in a 44-year-old
Coronal T1-weighted (A), proton-density–weighted
(B), and T2-weighted (C) images reveal that the lesion (arrows) is relatively dark on
all sequences and confined to the fat of the plantar heel pad

78. Giant cell tumor of tendon sheath
 is a localized form of pigmented villonodular synovitis
 usually benign lesions that arise from the tendon
sheath
 localized solitary subcutaneous soft tissue nodules

79. Plain radiograph
 they may cause pressure erosions on the underlying
bone in 10-20% of cases
 more commonly these masses arise from the palmar
tendons
 the mass itself is of soft tissue density
 periosteal reaction and calcification are uncommon

80. MRI
 T1WI
 low signal
 T2WI
 low signal
 Post contrast
 moderate enhancement
 GRE
 low and may demonstrate blooming

81. Case of Giant cell tumor of tendon sheath in 18 year-old
A well defined oval shape mass is seen anterior to the talus, extra articular in
position and underneath the tendon of the Extensor hallucis longus. The mass
displays low signal on T1, lower signal on T2 likely from hemosiderin deposition,
heterogeneous high signal on STIR, and avid enhancement on post contrast study.
No evidence of infiltration of the adjacent structures.

82. Retrocalcaneal Bursitis
 refers to inflammation of the retrocalcaneal bursa,
which lies between the antero-inferior calcaneal
tendon and posterosuperior calcaneus.
 It forms part of Haglund syndrome.
 Note – there is another 1 bursa i.e. subcutaneous
calcaneal bursa (between the tendon and the skin)
 rarely occurs in isolation and is almost always
associated with calcaneal tendinitis and/or Haglund
deformity
 Bursae - are small fluid-filled sacs lined by synovial
membrane with an inner capillary layer of synovial
fluid

83. causes
 calcaneal tendon injury: rupture or tendinitis
 inflammatory arthropathies: Reiter
syndrome, ankylosing spondylitis, rheumatoid
arthritis
 calcaneal fractures
 infectious bursitis

84. Imaging
 Plain film
 prominence of the posterosuperior calcanum can be
frequently seen 1
 decreased lucency of the retrocalcaneal soft tissue (Kager
triangle)
 Ultrasound
 bursa distension by a hypoechogenic fluid collection: > 1 mm
anteroposteriorly, > 7 mm craniocaudally, or > 11 mm
transversely is considered abnormal
 MRI
 fluid collection:
 T1: low signal
 T2: high signal
 STIR: high signal

85. Case of Retrocalcaneal Bursitis
Normal achilles tendon.
Fluid collection deep to tendon

86. Haglund syndrome
 Refers to Haglund triad of
1) insertional Achilles
tendinopathy
2) retrocalcaneal bursitis
3) posterosuperior
calcaneal exostosis
 Associated with calcaneal spurs
 Wearing high heels
 Stiffed backed shoes

87. Imaging
 Plain film
 loss of the Kager triangle due to retrocalcaneal bursitis
 Achilles tendon measuring over 9 mm in thickness 2
cm above the bursal projection due to Achilles
tendinopathy
 Postero-superior calcaneal spur
 MRI
 focal enlargement and abnormal signal at Achilles
tendon insertion segment
 retrocalcaneal and retroachilles bursal fluid collection
 calcaneal bony spur better appreciated on T1 sagittal
images
 marrow oedema of the posterior calcaneal tuberosity

88. Case of Haglund syndrome in 20 yrs. male
High signal near
achilles insertion

89. Achilles tendinopathy
 Macroscopically, tendinopathy results in
enlargement, disruption of fibrillar pattern and an
increase in tendon vascularity
 Ultrasound
 shows thickening and rounding of the affected portion of the
tendon. The cutoff value of 1 cm in anteroposterior diameter
is usually used for diagnosis.
 Additional signs include increased Kager’s fat pad
echogenicity.
 MRI
 shows increased intratendinous signal and tendon
enlargement, with oedema in Kager's fat pad in cases of
tendinosis.

90. Case of Achilles tendinopathy.
Patient with pain on dorsiflexion
Thickening of the achilles tendon
on the lateral view of the ankle can
be seen 5-6 cm above its insertion
into the calcaneum

91. Achilles tendon tears
 Pathology
 interstitial tears (parallel to the long axis of
the Achilles)
 partial tears
 complete tears.
 Location
 ruptures in the 'critical zone', which is a region
of relative watershed hypovascularity 2-6 cm
proximal to insertion

92. Kuwada classification of Achilles
tendon tear
 type I: partial ruptures ≤50%
 typically treated with conservative management
 type II: complete rupture with tendinous gap ≤3 cm
 typically treated with end-end anastomosis
 type III: complete rupture with tendinous gap 3 to 6 cm
 often requires tendon/synthetic graft
 type IV: complete rupture with defect of >6 cm (neglected
ruptures)
 often requires tendon/synthetic graft and gastrocnemius
recession

93. Case of Kuwada type I tear
thickened and hypoechoic right Achilles tendon with discontinuation of its deep
fibers at its insertion site at calcaneum with adjacent fluid.
Findings are suggestive of tendinopathy with partial thickness tear
involving less than 50% fibres

94. Case of Kuwada Type II tear
Achilles tear, just above the insertion