Ankle syndesmotic injury

Case contributed by Henry Knipe


Eversion injury. Positive external rotation test.

Patient Data

Age: 20 years
Gender: Male

No fracture. Skeletal alignment within normal limits. Soft tissue density partially obscuring Kager's fat pad most likely represents an accessory muscle. 


Complete rupture of the anterior inferior tibiofibular ligament. Hyperintensity of the distal tibiofibular syndesmosis with fiber disruption. Partial-thickness tear of the posterior inferior tibiofibular ligament with posterior tibial marrow edema at its insertion. Small ankle joint effusion. 

Incidental flexor digitorum accessorius longus extending into the tarsal tunnel. 

Case Discussion

High ankle or syndesmotic injuries occur in an "intercalary" manner with rupture of ligaments in order:

  • anterior inferior tibiofibular ligament
  • interosseous membrane
  • posterior inferior tibiofibular ligament

In intermediate injuries (i.e. incomplete rupture of all above structures), the x-ray may be normal and thus a normal x-ray does not exclude a high ankle injury.

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