The os peroneum is an accessory bone found within the peroneus longus tendon near the cuboid bone, while the os vesalianum is a rare accessory bone located near the base of the fifth metatarsal within the peroneus brevis tendon. The os peroneum is a more common accessory ossicle, whereas the os vesalianum can be confused with an avulsion fracture of the fifth metatarsal. Painful os peroneum syndrome typically involves the peroneus longus tendon, while a symptomatic os vesalianum can cause pain near the base of the fifth metatarsal.
