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.