This case demonstrates why a knowledge of common anatomical variants is essential.

The small bony chips lateral to the tip of the lateral malleolus represent an avulsion fracture while the well-corticated bony fragment adjacent to the medial aspect of the lateral malleolus tip could be mistaken for fracture if this was not the typical appearance and location for an accessory ossicle - the os subfibulare.

On the lateral projection, an os trigonum can be appreciated.