Fig. 1From: Ultrasound diagnosis and follow-up of a locked thumb metacarpophalangeal joint caused by radial sesamoid entrapment: a case reportAnteroposterior (a) and lateral (b) radiographs of the right thumb. The lateral radiograph shows a hyperextension posture of the metacarpal joint at approximately 30°. The abnormal location of the radial sesamoid (arrow) is difficult to recognize on radiographs because of bony overlapsBack to article page