An os peroneum is present but sits around 1cm proximal to its normal location along side the cuboid. On the lateral image a tiny fragment avulsed from the os peroneum is seen just distal to the cuboid. Given that the os peroneum is an ossicle that exists within the substance of the peroneus longus tendon, this x-ray appearance is consistent with complete rupture of the peroneus longus tendon just distal to the os peroneum.