Syndesmotic Injuries



High ankle sprain





- often unrecognised or misdiagnosed as lateral ligament injuries

- seen in ice hockey


1-15% of ankle sprains involve the syndesmosis


Mechanism Injury


Hyperdorsiflexion and forced external rotation





- anterior inferior tibiofibular ligament (AITFL)

- posterior inferior tibiofibular ligament (PITFL)

- interosseous ligament (provides only 10% of strength)


Ankle MRI AITFL PITFLSyndesmosis MRI Normal




High Ankle Sprain Clinical


1.  Tenderness over the AITFL


2.  Positive squeeze test 

- pain at ankle with squeezing the tibia & fibula at mid-calf


3.  Painful ER

- probably most reliable test

- neutral ankle with knee flexed 90o

- hold tibia in neutral

- externally rotate foot




Usually is no evidence of syndesmotic widening


Ankle AP Xray Syndesmotic MeasurementsAnkle Mortice Xray Syndesmotic Measurements


3 reliable indicators of syndesmotic widening


1.  Clear space 

- between the medial border of the fibula and the lateral border of the posterior tibia (incisura fibularis)

- measured 1 cm above the plafond

- distance should be approximately 5 mm or less on both the AP and mortise views in the normal ankle 


2.  Overlap of the fibula and the anterior tibial tubercle

- greater than 6 mm on the AP views

- greater than 1 mm on the mortise view


3.  Stress films for syndesmotic instability

- application of an external rotation and abduction force

- anesthesia is often required because of the painful nature of this examination


Syndesmosis stress view




May see HO / MO interosseous ligament


Ankle Interosseous HO






CT Syndesmosis normal




Highly accurate

- see disruption of ligament

- bone contusions posteromedial talus and posteromedial tibia


High Ankle Sprain MRI 1High Ankle Sprain MRI 2


Syndesmosis Injury T1Syndesmosis injury T2




Inspect the syndesmosis under external rotation stress test

- see widening > 2mm between tibia and fibula

- can also visualise AITFL and PITFL

- often a tibial chondral injury




1.  Xray evidence of widening


Syndesmosis InjurySyndesmosis TightropeSyndesmosis Tightrope 2



- diastasis screw / tightrope


2.  Syndesmotic injury with no widening


Takes 6 - 12 weeks to resolve

- impossible to strap

- WBAT but no impact sports 6 weeks


3.  Chronic injury / pain


Ogilvie-Harris Arthroscopy 1994

- arthroscopic debridement of sydesmosis and chondral injuries in 19 patients

- good results reported

- elimination of external rotation test