Chronic ankle instability with bilateral malleolar stress fractures

Case contributed by Henry Knipe
Diagnosis almost certain


Recurrent instability.

Patient Data

Age: 15-20 years
Gender: Male

Small ankle joint effusion. Marrow edema through the medial malleolus with linear lower signal intensity in a subchondral location. Mild marrow edema through the lateral malleolus with linear low signal intensity centrally. No periosteal edema. No osteochondral injury of the talar dome or distal tibial plafond. 

Chronic partial tear of the anterior inferior tibiofibular ligament and distal interosseous membrane. Posterior inferior tibiofibular ligament appears intact.

Anterior talofibular ligament is thinned compatible chronic partial tear with a few inferior fibers intact that appear mainly inserting onto an ossicle, which appears intra-articular between the medial surface of the distal fibula and the lateral talus. Calcaneofibular ligament is thinned. Deep deltoid ligament appears partially torn at the anterior fibers. Spring ligament complex is intact. Dorsal talonavicular and bifurcate ligaments are intact.

Mild distal tibialis tendinosis with a type I accessory navicular. 

Case Discussion

Chronic ankle instability is principally a clinical diagnosis. Imaging in this case reveals chronic syndesmotic and collateral ankle ligament injuries, intra-articular body, and bilateral malleolar stress fractures

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