Bowler's thumb: ultrasound diagnosis of a neuroma of the ulnar digital nerve of the thumb.

Bowler's thumb is a rare traumatic neuropathy of the ulnar digital nerve of the thumb. We present a case of bowler's thumb in a 21-year-old male recreational bowler who presented with a painful mass on the ulnar side of the right thumb. Magnetic resonance (MR) imaging of the hand was inconclusive.