Posterior ankle impingement: clarification and confirmation of the pathoanatomy.

The diagnosis of posterior hindfoot pain may prove to be elusive as there are many potential causes of hindfoot pain, including both soft tissue and osseous abnormalities. This is a case presentation of os trigonum syndrome, with the diagnosis suggested by magnetic resonance imaging (MRI), confirmed by ultrasound, and treated with os trigonum resection. Specific findings of os trigonum syndrome can be seen on MRI, including bone marrow edema pattern and high signal intensity in the synchondrosis as well as in the surrounding soft tissues. Diagnostic injections performed with imaging guidance can help confirm the diagnosis in equivocal cases. Diagnostic and interventional imaging procedures can help confirm the diagnosis of os trigonum syndrome in a patient presenting with hindfoot pain.