Differential diagnosis in a professional basketball player with foot pain: is it an avulsion fracture or an os supranaviculare?

The os supranaviculare is an accessory bone located on the dorsal aspect of the talonavicular joint close to the midpoint. This rare incidental skeletal variant has an estimated prevalence of 1%. It may rarely become symptomatic and should not be confused with cortical avulsion fractures of navicular or talar head. We present the case of a 25-year-old professional basketball player with pain on the dorsum of his right foot after twisting his ankle during a regular season match. Magnetic resonance imaging findings of the player's foot represented a flake of bone on the superior part of the talar head. The differential diagnosis and clinical outcome of this unusual case are briefly discussed.