Extensor Tendon Injury [Hand]


The extensor tendons are strong smooth cords that straighten the fingers by connecting the muscles of the forearm and hand to the bones in the fingers and thumb.

At the base of the finger, the long tendon from the forearm muscle is joined by the short tendons from the small muscles in the hand to form a complicated sheet of tendon fibres over the back of the finger.   This sheet has a central band that straightens the middle joint and two lateral bands that separate and join together again to straighten the end joint

The extensor tendons are just under the skin and are easily injured by any cut across the back of the wrist hand or fingers. The tendons are especially vulnerable where the cut is over the back of the joints of the fingers.


The tendons can also be torn by closed injuries such as stubbing the finger, usually at the end joint (mallet finger) or at the middle joint (boutonnière deformity).

  • A cut across the back of the wrist, hand or finger.
  • Inability to fully straighten the finger or thumb.
  • The finger or thumb drooping downwards
  • Pain on trying to straighten the finger or thumb.

A hand surgeon will test the tendons to ascertain their integrity and decide if a repair is needed.  X-rays may be taken if the injury was caused by glass or if damage to a joint is suspected.  Occasionally, ultrasound or MR scans are needed to give more information about the tendon.