Os vesalianum is an accessory bone of the foot located proximal to the fifth metatarsal and found within the peroneus brevis tendon.
Location & Anatomy
Proximity: It sits proximal to the base of the fifth metatarsal — that’s the long bone on the outer side of your foot leading to the pinky toe.
Embedded in Tendon: Specifically, it’s located within the peroneus brevis tendon, which inserts on the tuberosity of the fifth metatarsal.
Appearance: Radiographically, it looks like a small, oval or round bone with smooth, corticated edges, indicating it’s a true ossicle (not a fracture).
Clinical Significance
Most cases are asymptomatic — meaning, people often don’t know they have it.
But when symptoms do appear (usually after trauma or overuse), it might cause:
Lateral foot pain (especially near the base of the 5th metatarsal)
Swelling or tenderness over the lateral border of the foot
Confusion with fractures if misdiagnosed
