The term mallet finger describes an injury, which results in an inability to extend the end of the finger. The injury is often caused by relatively benign trauma, such as catching finger on clothing. It can also be caused by a forceful blow to an extended finger, for example from a cricket ball, or as a consequence of a fall from a bicycle.
Patients report that the end of the finger droops. The tendon responsible for lifting the distal phalanx (the last bone in the finger), is torn or stretched. A small fragment of bone may have pulled away with the tendon, and very-occasionally the normal position of the finger bones can become disrupted, with partial dislocation at the distal inter-phalangeal joint.
The majority of mallet finger injuries can be described as closed, and no disruption of the skin. Less commonly the injury can be described as the skin can break, or a cut across the top of the finger, for example from a knife, or from broken glass, can result in a divvision of the tendon.