Mallet injury is an injury that causes a typical mallet deformity in the finger.
This causes a rupture of the extensor tendon or an avulsion fracture of the base of the distal phalanx. This frequently happens in basketball or volleyball, when the ball hits the point of the finger, causing it to flex forcibly at its tip. The patient presents with a crooked finger, bent at the last joint of the finger the so-called mallet deformity. If the tendon is ruptured, and there is no fracture, the injury is quite painless. However, the patient is unable to extend or straighten the DIP joint on his own.