This document provides an overview of ankle radiography including: - The Ottawa Ankle Rules for determining when radiographs are needed - Common radiographic projections of the ankle including AP, mortise, and lateral views - Measurements taken from the different views to assess for fractures and ligament injuries - Stress tests that can be performed under fluoroscopy to evaluate ligament integrity - Classification systems for common ankle fractures like the Danis-Weber and Pott's classifications

1. ANKLE JOINT
RADIOGRAPHY
By Dr. Nikhil Murkey

2. The Ottawa Ankle Rules (OAR)
• The commonly used criteria for predicting which
patients require radiographic images.
• Radiographs are only required for those patients
with
• tenderness at the posterior edge or tip of the
medial or lateral malleolus.
• inability to bear weight (4 steps) either
immediately after the injury or in the
emergency room.
• pain at the base of the fifth metatarsal

3. Projections
• Three main projections:
• AP
• Identifies fractures of malleoli, distal tibia/fibula, plafond, talar
dome, body and lateral process of talus, calcaneus.
• Mortise
• Ankle 15-35 degrees internal rotation (20-25-degrees
commonly used).
• Evaluate articular surface between talar dome and mortise.
• Lateral:
• Identifies fractures of anterior/posterior tibial margins, talar
neck, displacement of talus.
• Other views like AP ankle plantar flexion view, medial oblique
foot view, AP of proximal fibula, etc. may also be required in
conjunction with above mentioned views.

4. Antero-posterior view
The ankle is slightly
dorsiflexed so that the
plantar surface of the foot is
perpendicular to the
film, which brings the
weight-bearing talar surface
into optimum tangential
projection. Internally rotate
the lower leg so that a line
through the malleoli is
parallel with the film surface.

6. Measurements in AP view
• Tibial shaft line (A). A line is drawn through
and parallel to the tibial shaft.
• Medial malleolus line (B). A line is drawn
tangential to the articular surface of the
medial malleolus.
• Lateral malleolus line (C). A line is drawn
tangential to the articular surface of the
lateral malleolus.
• Talus line (D). A line is drawn tangential to
the articular surface of the talar dome.
• Tibial angle (I). The angle is formed
medially between the medial malleolus line
and talus line.
• Fibular angle (II). The angle is formed
laterally between the lateral malleolus line
and talus line.
Angle Average (°) Min (°) Max (°)
These angles will be altered in fractures of
Tibial (I) 53 45 65 the malleoli, ankle mortise instability, and
Fibular (II) 52 43 63 tibiotalar slant deformities.

7. Measurements in AP view
• Tibio-fibular clear space:
- tibiofibular clear space is the cartilaginous space
between lateral border of posterior tibia (incisura fibularis) &
medial border of fibula, measured 1 cm above the joint line;
- normally the clear space is less than 5-6 mm on both
AP and Mortise views. (increase indicates syndesmotic and
deltoid disruption).
• Tibio-fibular overlap:
- should be greater than 6 mm or 42% of fibular
width.
• Superior clear space: Difference in width of superior clear
space between medial & lateral sides of joint should be < 2
mm

8. Measurements in AP view
Talar Tilt:- difference in width of superior
clear space between medial & lateral sides
Tib-fib Clear Space > 5mm or of joint should be < 2 mm
Tib-fib Overlap < 10mm
may indicate syndesmotic injury > 2 degrees angulation may indicate
medial or lateral disruption

9. Specialized Projections (AP)
• Plantar flexion view (lazy AP view): For subtle fractures of the talar
dome, including osteochondritis dissecans, plantar flexion will often
demonstrate the fracture site as the posterior articular surface comes
into view.
• Inversion-eversion stress views: The stress is induced by a third
person, who wears lead gloves and lead apron, or by the patient, who
holds a strap that is looped around the sole of the foot. The views
should be performed and measurements compared bilaterally.
• Joint stability is defined by less than 5 deg difference between the injured
and uninjured sides.
• Weight-bearing AP view: Performed AP and weight bearing with a
horizontal beam. This is especially valuable in showing degenerative
decreased joint space and chronic instability with lateral talar tilt or
lateral shift. Diastasis of the distal tibiofibular syndesmosis may also
be more apparent as a widened joint with lack of tibiofibular overlap.

10. Radiographic Stress Tests of the Ankle
• Talar Tilt Stress Test
• Contralateral ankle used for
comparison
• Line is drawn across the talar
dome and tibial vault
• Degree of lateral opening angle
is measured
• Normal tilt is less than 5 deg
• Considered abnormal if tilt
greater than 10 deg (indicator
of lateral ligament injury).
• Standing Talar Tilt Stress Test:
• may be more sensitive
• Patient stands on an inversion
stress platform with the foot
and ankle in 40 deg of plantar
flexion and 50 deg of inversion
• External Rotation Stress Test
Evaluates syndesmoses & deep
deltoid ligaments

11. Lateral View of the Ankle
• The lateral surface of
the ankle is in contact
with the film, with the
foot slightly dorsiflexed.
Cross the opposite leg
over the leg being
examined, and support
the opposite knee to
avoid rotation of the
ankle.

13. Lateral View of the Ankle
Posterior tibial Dome of the talus:
tuberosity fractures centered under
& direction of fibular and congruous
injuries can be with tibial plafond
identified
Avulsion
fractures of
the talus by
the anterior
Any deformity capsule can
to the be identified
talus, calcaneu
s or subtalar
joint

14. Measurements in Lateral view
• Heel-Pad measurement:
• The shortest distance between
the plantar surface of the
calcaneus and external skin
contour is measured.
• Increased skin
thickness, especially of the heel
pad, is a frequent accompanying
feature of acromegaly.
• Achilles tendon thickness can be
assessed on a lateral view at 1-2
cm above the calcaneus and is
normally 4-8 mm in dimension.
Edema from inflammatory arthritis
can thicken the ligament.
Average Maximum
Sex (mm) (mm)
Male 19 25
Female 19 23

15. Measurements in Lateral view
Boehler’s Angle:
• The three highest points on the
superior surface of the
calcaneus are connected with
two tangential lines. The angle
formed posteriorly is then
assessed.
• The angle formed posteriorly
averages between 30° and 35°
in most normal subjects but
may range between 28° and 40°
• The most common cause for an
angle < 28° is a fracture with
displacement through the
calcaneus. Dysplastic
development of the calcaneus
may also disturb the angle.

16. Specialized Projections (Lateral)
• Drawer view: A third person, who wears lead gloves and a lead
apron, stabilizes the tibia and pulls the hind foot forward.
• Flexion-extension (dancer views): These can be performed with
or without weight bearing with the foot on maximal plantar and
then dorsiflexion for demonstrating bony impaction anteriorly
and posteriorly as a sign of impingement syndromes.
• Lunge’s view: Performed weight bearing in plantar flexion, the
view demonstrates the degree of impaction of the anterior
tibial margin to the neck of the talus, as part of the assessment
for anterior impingement syndrome.
• Lazy lateral: The posterior tibial margin is a frequent site of
fracture and can be best demonstrated in an off-lateral
projection, with slight external rotation of the foot. In
addition, signs of posterior impingement syndrome can be
shown to advantage at the posterior talus and os trigonum.

17. Radiographic Stress Tests of the Ankle
• Anterior Drawer
Test
• The anterior
drawer test
evaluates ATFL
integrity.
• Abnormal
anterior
translation is
between 5 to 10
mm, or 3 mm
more than other
side

18. Mortise view
• The ankle is slightly
dorsiflexed so that the
plantar surface of the foot
is perpendicular to the film.
The lower leg is then
internally rotated so that
the intermalleolar line
forms an angle of 35° with
the film.
• The amount of medial
rotation is open to
variation, with some
advocating views at
20°, 35°, and 45° to
demonstrate the mortise

19. Mortise X-Ray
• This is an important
view in the
assessment of the
post-traumatic ankle
for detecting subtle
fractures of the distal
fibula, posterior
tibia, talar dome, and
base of the fifth
metatarsal

20. Measurements in Mortise view
• Medial clear space
• Between lateral border of
medial malleous and medial
talus
• <4mm is normal
• >4mm suggests lateral shift of
talus
• Tibiofibular overlap:
should normally be more than
1 mm

21. Measurements in Mortise view
• Talo-crural angle is formed by:
- line drawn parallel to articular
surface of distal tibia
- line connecting tips of both
malleoli (intermalleollar line).
- this angle is normally 8 - 15
degrees.
- alternative method:
- angle formed by perpendicular
to tibial articular surface &
intermalleollar line.
- this angle is normally between
75 and 87 degrees.
- Shortening:
- by either method this angle
should be within 2 - 5 deg of
opposite side.
- difference of greater than this
indicates fibular shortening.

22. Measurements in Mortise view
• Talar tilt
• line drawn parallel to articular
surface of distal tibia;
- second line drawn
parallel to talar surface
• Both lines should be parallel to
each other and normal tilt angle
is 0 deg (range 1.5 to 1.5 deg)
• alternative method:
- angle between
intermalleolar line & each of
these two articular surface lines
is measured;
- difference between these
two angles is the talar tilt;

23. Syndesmotic disruption:
• On the AP radiograph syndesmotic disruption
is indicated by a
• Tibial Clear Space >5mm
• Tibio Fibular Overlap <10mm
• On the mortise view a
• Tibio Fibular Overlap <1mm

24. AP View:
Widened medial clear
space
Mortise View:
Open mortise
(decreased tib-fib
overlap)
= Syndesmotic injury
= Surgical referral

25. 25 y/o volleyball player
“landed wrong” on the
right foot, “hurting” the
ankle
Radiograph shows positive
talar tilt stress view
Lateral
ligament
tears
-ATFL
-CFL

26. 25 y/o male tennis player
“torqued” his right ankle
Grade III ATFL
ankle sprain

27. Ankle Fracture Classification
• Danis-Weber Classification
• Defined by location of the
fracture line
• Type A: below the tibiotalar
joint
• Type B: at the level of the
tibiotalar joint
• Type C: above the tibiotalar
joint
• Syndesmotic ligament
compromise
• Lauge-Hansen Classification
• Infrequently used, clinically;
mostly academic

28. AO classification:
• Similar to Danis-Weber scheme
• Takes into account damage to other structures
(usually medial malleolous)
• ~2 pages of classifications

29. Pott’s classification:
• First degree
• unimalleolar
• Second degree
• bimalleolar
• Third degree
• trimalleolar

30. Weber Type A
lateral
malleolar
fracture
Treat
conservatively

31. 28 y/o M who “twisted”
his left ankle while
playing basketball 1 day
ago
Danis-Weber Type B
fibular ankle fracture

32. Mortise view:
Weber C
fracture with
open mortise
and widened
medial clear
space
= deltoid &
syndesmotic
ligament
tears, with
fracture
= surgical
referral

33. Fractures
• Medial or Lateral Malleolar fracture
• Bimalleolar fracture
• Trimalleolar fracture
• Pilon fracture
• Pott’s fracture
• Maisonneuve’s fracture
• Dupuytren’s fracture
• Tillaux fracture
• Toddlers fracture

34. • MEDIAL MALLEOLUS
FRACTURE AND
ASSOCIATED DISTAL
FIBULA FRACTURE.
AP Ankle. Note the
medial malleolus fracture
(arrowhead) and an
oblique fracture of the
distal fibula, along with
lateral displacement of
the talus. The linear
subchondral radiolucency
in the talar dome
(arrows) is a radiographic
sign for an intact blood
supply to the talus
(Hawkin’s sign), which
represents the
unlikelihood of
complicating avascular
necrosis.

35. • LATERAL MALLEOLUS
FRACTURE.
Medial Oblique Ankle.
Note the most common
fracture of the lateral
malleolus is an oblique
fracture extending upward
(arrow). This fracture is best
seen on the medial oblique
projection
• These fractures occurs as
a result of outward or
external rotation of the
foot and is best observed
on the medial oblique
projection as a
radiolucent oblique line
with adjacent soft tissue
swelling (McKenzie’s sign)

36. BIMALLEOLAR
FRACTURE.
AP Ankle.
Note the
characteristic
transverse
fracture through
the medial
malleolus
(arrow), along
with a spiral
fracture of the
lateral malleolus
(arrowhead).

39. Trimalleolar Fractures
• Unstable
• Multiple ligamentous injuries
• Usually involves syndesmosis
• Treatment
• Posterior slab
• Urgent orthopedic consultation
• ORIF

40. Pott’s Fracture
Pott’s fracture, as classically
described, is a partial
dislocation of the ankle, with
fracture of the fibula within
6-7 cm above the lateral
malleolus and rupture of the
distal tibiofibular ligaments
of the ankle.

42. Pilon (tibial plafond) fractures
• Fracture of distal tibial
metaphysis
• Often comminuted
• Often significant other injuries
• Mechanism
• Axial load
• Position of foot determines injury
• Treatment
• Unstable
• X-ray tib/fib & ankle
• Orthopedic consultation
Source:Rosen

44. Maisonneuve Fracture
• This fracture is caused by forceful
inversion and external rotation of
the ankle.
• This motion forces the talus laterally
against the fibula ( d/t either deltoid
ligament tear or avulsion fracture of
medial malleolus), initially producing
rupture of the inferior tibiofibular
syndesmosis. As the force is
maintained, the fibula, freed from
the tibia, continues to be displaced
laterally and posteriorly. The
superior tibiofibular joint, remaining
intact, secures the proximal fibula so
that the long lever of the fibula
produces a fracture of the fibula in
its proximal third.

45. Dupuytren’s
fracture,
is a fracture of the
distal fibula (lateral
malleolus) with rupture
of the distal tibiofibular
ligaments, diastasis of
the syndesmosis,
lateral dislocation of
the talus, and
displacement of the
foot upward and
outward.

46. Dupuytren’s fracture
• Mechanism similar
to Maisonneuve
fracture.
• Posterior tib-fib
ligament ruptures
• Interosseous
membrane rips
• Gross diastasis

48. Tillaux Fracture
• Salter Harris III fracture involving avulsion of
anterolateral tibial epiphysis.
• Occurs in older adolescents, after the middle and
medial parts of epiphyseal plate has closed, but before
the lateral part closes (usually 12 to 15 yrs of age).
• Fracture occurs after medial part of the epiphyseal
plate has closed, but before the lateral part closes;
resultant fracture through epiphyseal plate runs across
epiphysis and distally into the joint, creating SH type 3
or 4 fracture.
• External rotation forces stresses on anterior
tibiofibular ligament, causing avulsion of distal tibial
epiphyseal plate anterolaterally;
further lateral rotation causes displacement of
fracture.

49. Toddler’s Fracture
Toddler’s fracture, an
undisplaced spiral fracture of
the tibia, occurs in children from
9 months to 3 years of age. It is
caused by a fall or by the child
getting a foot caught between
the slats of the crib and then
rolling over. The baby, often too
young to verbalize its
complaints, may evidence only a
mysterious refusal to bear
weight on the extremity.

50. Ankle effusion: tear drop sign
NORMAL WITH EFFUSION
An ankle effusion suggests a significant injury to the ankle joint. The anterior
and posterior extra-capsular region of a normal ankle joint should appear as a
fat-like density. In the presence of an ankle effusion, the capsule can become
distended and may appear to have a more fluid-like density

51. Soft Tissue Swelling over the Lateral Malleolus
NORMAL MILD MODERATE SEVERE
• An extreme amount of soft tissue swelling does not necessarily indicate a
fracture is present and is frequently seen in severe sprain injuries
(tendon/ligament injuries).
• In equivocal cases where you are suspecting a lateral malleolus fracture and
there is little or no soft tissue swelling laterally, you would lean towards a
diagnosis of no fracture.

52. Achille's Tendon Rupture
This patient has a
Normal Kager's fat pad with
ruptured Achilles tendon
clearly delineated normal Achilles
(white arrow). Note the
tendon
changes in Kager's Fat Pad
(black arrow)

53. This patient presented to the
Emergency Department following
a fall from a ladder. Note that
Kager's fat pad is abnormal
showing increased density and
indistinct margins. There also
appears to be a large ankle
effusion. These soft tissue signs
should lead you to undertake a
careful examination of the bony
anatomy. The patient has a
fractured calcaneum.

54. This 55 year old lady presented
to the Emergency Department
with a boggy infected area of
skin over her Achilles tendon.
The patient was referred for
ankle radiography with a view
to establishing whether there
was an underlying
osteomyelitis. The infection
clearly involves the deeper soft
tissues with almost complete
obscuration of Kagers fatpad.
There is no evidence of
osteomyelitis.

55. This patient presented to the ED
following a sports injury to the left
ankle. On examination, the patient
was unable to weightbear . Swelling
over the lateral malleolus of the
ankle was visible clinically and
radiographically.
The lateral view demonstrates
* an ankle effusion- (white arrows)
* abnormal Kager's fat pad (grey arrow)
* suggestion of fracture or accessory
ossification centre (os subfibulare)- black
arrow
The combination of patient history, clinical
signs, soft tissue signs and equivocal
evidence of a fracture was sufficient for
the radiographer to perform additional
views

56. The orientation of the
possible fibula fracture
demonstrated on the
lateral projection image
suggested that an AP ankle
position with cephalic tube
angulation might align the
X-ray beam with the plane
of the fracture.

57. Diagnosis?
Charcot’s foot

58. Thank you.