Ankle Injuries: A Sprained Ankle ?
Radiology Cases in Pediatric Emergency Medicine
Volume 3, Case 3
Alson S. Inaba MD
Kapiolani Medical Center For Women And Children
University of Hawaii John A. Burns School of Medicine
     A 17 year old male presents to the Emergency 
Department one day after sustaining a "twisting" injury 
to his left ankle while playing soccer.  The patient 
claims to have sustained a "twisted ankle" while he was 
running towards the goal.  He does not recall exactly in 
which direction his ankle twisted.  He did not feel or 
hear any "snaps," "pops," or "clicks."  Although he was 
able to bear some weight on the ankle immediately after 
the injury, today he has much more pain and swelling 
about the anterior and lateral aspect of the affected 
ankle.  Overnight he did not elevate the ankle nor did he 
apply any ice to the injured ankle.  He denies sustaining 
any other injuries and has not sustained any previous 
injury to his left ankle.  This morning he is unable to 
walk on the ankle secondary to increased pain and 
     On examination, he is barely able to bear any weight 
on the affected ankle secondary to pain.  There is 
obvious swelling (without ecchymosis) to the anterior 
and lateral aspect of the ankle joint.  Distally, his toes 
are pink, with brisk capillary refill and intact sensation to 
light touch.  Tenderness can be elicited by palpation 
over the anterior aspect of the ankle joint (Refer to 

Review area of tenderness.

     The black arrow points to the region of maximum 
tenderness.  There is no tenderness along the inferior 
tip of the lateral malleolus or over the bony prominence 
of the lateral malleolus.  There is no tenderness along 
the medial aspect of the ankle or along the proximal 
aspects of both the tibial and fibular shafts.  The 
squeeze test over the distal tibia-fibula region does not 
produce any pain.  Both the anterior drawer and talar tilt 
maneuvers are within normal limits when compared to 
the nonaffected ankle. 

     a)  Has this patient sustained a typical ankle sprain?
     b)  What is the typical mechanism of injury for the 
majority of ankle sprains sustained during sporting 
     c)  Which ankle ligament is most commonly sprained 
during an inversion injury, and where on the ankle 
should one palpate to check for tenderness to this 
     d)  Describe the anterior drawer test and what 
specifically does this maneuver test for?
     e)  Describe the talar tilt test and what specifically 
does this maneuver test for?
     f)  What is the syndesmosis, and how does one 
examine for possible syndesmotic injuries?

Discussion & Teaching Points:
     Ankle injuries are one of the most common 
sports-related orthopedic injuries seen in the 
Emergency Department.  These types of injuries are 
most commonly sustained in patients between 15 - 35 
years of age.  The majority of ankle sprains (up to 85%) 
are due to inversion injuries while only 15% are due to 
eversion-related injuries.  There are 3 lateral ankle 
ligaments and one broad, fan-shaped medial ligament.

Review the ligaments.

     Although ankle sprains are common in older 
adolescent patients and young adults, isolated ankle 
sprains  are not very common in younger children and 
in preadolescent patients.  The physis (growth plate) in 
these younger children is much weaker than the 
surrounding ligaments, and is thus more susceptible to 
injury.  Therefore in the pediatric population, injuries 
involving the growth plates (Salter-Harris injuries) must 
also be considered in addition to ligament sprains. 
     The anterior talofibular ligament (ATFL) is the 
weakest of the 3 lateral ligaments and is the most 
commonly injured of the lateral ankle ligaments.  (Note 
that ATFL can also stand for anterior tibiofibular 
ligament, however, in this case, ATFL will be used to 
stand for anterior talofibular ligament.)  65% of lateral 
ligament sprains are confined to the ATFL alone, while 
20% have concomitant calcaneofibular ligament (CFL) 
tears.  The ATFL can be palpated just inferior and 
anterior to the distal most aspect of the lateral 

Review ATFL location.

     The white arrow points to the region of the ATFL.  
Because the patient in this case has point tenderness in 
an area other than over the ATFL, he has therefore not 
sustained a typical ankle sprain.  In comparison to 
these lateral ligaments, the medial, deltoid ligament has 
a fair degree of elasticity and is much more resistant to 
     Most injuries also occur while the ankle joint is in 
plantar flexion rather than in dorsiflexion.  Anatomically, 
the talar dome is wedge-shaped, with the anterior 
aspect of the talus being wider than the posterior 
aspect.  During dorsiflexion, this wider, anterior aspect 
of the talus is engaged within the mortise (formed by 
the distal tibia and fibula), and the joint is very stable.  
However during plantar flexion, the narrower, posterior 
aspect of the talus becomes engaged in the ankle 

Review joint space diagram.

     Note the obvious widening of the joint space during 
plantar flexion on the left compared to dorsiflexion on 
the right.  Thus, with this understanding of the 
articulation of the talus within the mortise, it is not 
surprising that most ankle injuries occur while the ankle 
is in plantar flexion, rather than in dorsiflexion.
     The last part of the clinical examination of an injured 
ankle involves assessing the stability of the ankle joint.  
The two maneuvers that can be performed to assess 
the stability of the ankle joint are the anterior drawer 
and talar tilt maneuvers.  Keep in mind that the ability to 
perform these tests and the results immediately after an 
injury may be limited by swelling, pain and muscle 
spasm.  Do not attempt to perform either of these tests 
if there is an obvious deformity of the ankle suggestive 
of a possible ankle fracture.
     The ATFL ligament normally prevents the anterior 
subluxation of the talus from the mortise.  The talus 
may be subluxed anteriorly whenever the ATFL is 
partially ruptured (second-degree sprain) or completely 
ruptured (third-degree sprain).  The anterior drawer 
maneuver assesses the integrity of the ATFL.  Since 
the ATFL is usually the first ligament to be injured in a 
typical inversion injury, some physicians feel that if this 
anterior drawer test is negative, it is then unnecessary 
to perform the talar tilt maneuver (since the talar tilt 
stress test is positive only if both the ATFL and the CFL 
are injured).  To perform the anterior drawer maneuver, 
the patient can either be supine or sitting down, with the 
ankle in neutral position.  One hand of the examiner 
cups the heel of the affected ankle (and attempts to pull 
the foot anteriorly), while the other hand braces along 
the anterior aspect of the lower leg.

Review drawer sign maneuver.

     If the foot of the affected ankle can be pulled forward 
by more than 3 - 5 mm (or if the affected ankle can be 
subluxed more forward than the nonaffected side), 
suspect a rupture of the ATFL.    
     The talar tilt test assesses the integrity of the CFL.  
To perform this maneuver the patient can again be 
either sitting down or supine, with the ankle in neutral 
position.  While one hand of the examiner holds the 
lower leg stationary, the other hand gently attempts to 
invert the ankle.

Review talar tilt maneuver.

     Greater than 10 degrees of difference in the talar tilt 
when compared to the nonaffected side is suggestive of 
an injury to the CFL.
     Proximal to the lateral and medial ankle ligaments, 
the distal tibia and distal fibula are connected to each 
other by a series of tough fibrous structures collectively 
referred to as the tibiofibular syndesmosis.  The three 
individual components which make-up this syndesmosis 
include:  a) anterior tibiofibular ligament, b) posterior 
tibiofibular ligament, and c) intraosseous membrane.

Review syndesmosis anatomy.

     Note that on this diagram, the PTFL stands for the 
posterior talofibular ligament (not the posterior 
tibiofibular ligament).  The posterior tibiofibular ligament 
is NOT drawn on this diagramatic view.
     Clinically one can check for injuries of the tibiofibular 
syndesmosis by the squeeze test.  To perform this test, 
the examiner firmly grasps the patient's lower leg 
(around the lower aspect of the calf), and gently 
squeezes the tibia and fibula together.

Review squeeze test.
     Provided that there are no fractures of the tibial or 
fibular shafts, if ankle pain can be elicited by this 
squeeze maneuver, one should suspect an injury to one 
or more of the components of the tibiofibular 

     a)  What are some clinical criteria that would warrant 
a radiographic examination of an injured ankle?
     b)  What are the 3 standard radiographic views that 
are obtained on patients with ankle injuries?
     c)  When do the distal tibial and distal fibular 
epiphyses appear, and by what age do these epiphyses 
fuse to the adjacent metaphyses?

Discussion & Teaching Points
     It is estimated that over $500 million dollars are 
spent each year on ankle radiographs.  However the 
majority (up to 85%) of these radiographs are negative.  
In 1992,  a Canadian study suggested the adaptation of 
the Ottawa ankle rules, which could be used to order 
ankle radiographs based on selected clinical criteria.  It 
is important to remember that this study excluded 
patients younger than 18 years of age.  Therefore, 
since the Ottawa study did not include growth plate 
injuries, one should not strictly adhere to these rules 
when deciding whether or not to obtain a radiograph on 
a pediatric patient. Based on these Ottawa ankle rules, 
clinical indications that would warrant a radiographic 
evaluation would include any one of the following 
     a)  Inability to bear weight both immediately after the 
injury and in the Emergency Department.
     b)  Bony tenderness over the posterior edge, tip or 
distal 6 cm of the lateral malleolus.
     c)  Bony tenderness over the posterior edge, tip or 
distal 6 cm of the medial malleolus.
     d)  Tenderness over the base of the 5th metatarsal.

     A complete, standard radiograph examination of the 
ankle should include 3 views (AP, lateral, and a mortise 

Review ankle views.

     a)  AP view:  There are several findings that can be 
observed on the AP view.  The tip of the lateral 
malleolus normally extends more distally than the tip of 
the medial malleolus.  The syndesmosis of the ankle 
joint normally causes an overlap of the medial aspect of 
the distal fibula and the lateral aspect of the distal tibia 
on this AP view.  Therefore, subtle fractures involving 
either the lateral aspect of the distal tibia or the medial 
aspect of the distal fibula (i.e., between the tibia and 
fibula) may be difficult to visualize on this AP view alone 
because of the overlap.  It is a common pitfall to miss a 
Salter Harris Type III fracture of the distal lateral tibia 
because it is obscured by the overlapping fibula.
     b)  Lateral view:  On a true lateral view, the malleoli 
should be superimposed upon one another.  The lateral 
view provides a better view of the posterior aspect of 
the distal tibia and fibula, the talus, calcaneus and the 
base of the 5th metatarsal.
     c)  Mortise view:  To obtain a better view of the 
ankle mortise, the patient's leg must be internally 
rotated just enough so that the lateral malleolus (which 
is normally posterior to the medial malleolus), is on the 
same horizontal plane as the medial malleolus, and a 
line drawn through both malleoli would be parallel to the 
tabletop.  Usually this only requires approximately 10 - 
20 degrees of internal rotation.  In other words, whe
n viewing the mortise view, the tibia and fibula must be 
viewed without superimposition on each other.  This 
mortise view represents a true AP projection of the 
ankle mortise and also provides a good visualization of 
the talar dome (to rule-out osteochondral talar dome 
fractures).  The clear joint space [formed by the 
talofibular joint, the superior space between the dome 
of the talus & the tibial plafond (the inferior articulating 
surface of the tibia) and the tibiotalar joint] should all 
uniformly measure 3 - 4 mm.  A difference of greater 
than 2 mm (i.e., the joint space width varies by more 
than 2 mm.  Eg., Joint space measures 2 mm at lateral 
part of joint and 5 mm at medial side of joint.) is 
suggestive of mortise instability.

     If all of the above 3 views appear normal in a patient 
with a high clinical suspicion of a fracture, one should 
then obtain internal and external oblique views of the 
ankle to obtain additional views of the distal tibia and 
distal fibula.  To obtain such views, the patient's leg is 
rotated 45 degrees internally, then 45 degree externally.
     The epiphyses of the distal tibia and fibula both 
appear by 2 years of age.  The physis of the distal tibia 
fuses to its adjacent metaphysis by 18 years of age.  
The physis of the distal fibula fuses to its adjacent 
metaphysis by 20 years of age.  Therefore, growth plate 
injuries should still be considered as a possibility in any 
patient up to 20 years of age.  If one is unsure if a 
radiolucent line involving the distal tibia or fibula 
represents either a physis or an actual fracture, 
consider obtaining a comparison view of the 
nonaffected ankle.         
     An x-ray of the patient's ankle was obtained.  
Review our patient's ankle radiographs.     
     How would you interpret these 2 views?  Oblique 
and mortise views were also obtained because of the 
physical exam findings.

Review mortise view.

     What does this mortise view reveal that may not 
have be very evident on the 2 previous views?

     Radiographic interpretation:   There is a moderate 
amount of soft tissue swelling over the lateral malleolus.  
The AP and lateral views do not reveal any obvious 
fractures.  However, there is a subtle widening of the 
medial aspect of the distal fibular growth plate (physis) 
on the mortise view.  Comparative views and/or stress 
views would confirm that this is a fracture versus a 
normal growth plate closure.

     a)  Does this patient require immediate orthopedic 
intervention or can he be sent home from the 
Emergency Department with an out-patient orthopedic 
     b)  If you would send this patient home, what type of 
dressing or splint would you apply?

Discussion & Teaching Points:
     This patient has sustained a nondisplaced 
Salter-Harris type I fracture of the distal fibula (lateral 
malleolus).  Clinical and or radiographic criteria that 
would warrant immediate orthopedic intervention 
     a)  An open fracture. 
     b)  Any type of injury with neurovascular 
     c)  Any unstable fracture (which would be difficult to 
adequately immobilize in a splint). 
     d)  Any ankle dislocation (which tends to carry a high 
risk of neurovascular compromise).  

     Since this patient does not have an open fracture, 
dislocation or evidence of neurovascular compromise, 
his stable fracture does not require an immediate 
orthopedic intervention.  Therefore, this patient may be 
immobilized in an appropriate splint and sent home with 
an orthopedic referral for definitive casting.  A posterior 
ankle splint would probably not be adequate 
immobilization by itself for an ankle fracture.  

Review splint types.

     The posterior splint is on the left.  The sugartong (or 
stirrup) splint is on the right.  An ankle stirrup splint 
would provide better immobilization, since it protects 
against inversion-eversion and to some degree also 
protects against a fair degree of flexion-extension.
     The stirrup splint can also be combined with the 
posterior splint to provide maximal immobilization and 
protection against further trauma to the injured ankle.  
Patients should be told to refrain from weight-bearing 
(use crutches) and to elevate the injured extremity as 
much as possible.

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Web Page Author:
Loren Yamamoto, MD, MPH
Associate Professor of Pediatrics
University of Hawaii John A. Burns School of Medicine