Entrapment of the flexor hallucis longus tendon following ankle arthrodesis.

Impingement following arthroscopic ankle arthrodesis has not been reported in the literature previously. We present a case report of a 68-year-old male 9 months following an uncomplicated arthroscopic ankle fusion presenting with persistent posteromedial ankle pain. Flexor hallucis longus (FHL) tendon impingement resulting from a prominent os trigonum was identified. This was successfully treated utilising hindfoot endoscopy with excision of the os trigonum and FHL release.