Flexor Tendon Injury

Movement in the hand and fingers is controlled by a system of muscles and tendons located in the forearm, wrist and hand. Tendons connect muscles to bone. When a muscle contracts, or tightens, the muscles power the tendons to move our bones. The ability to bend our fingers to make a fist is controlled by the flexor tendon.


Most commonly, a flexor tendon injury results from lacerations (cuts). A laceration to the forearm, hand or wrist can result in injury to the flexor tendons. When a flexor tendon injury happens there can be inability to bend the fingers, thumb or wrist. Even small lacerations can result in significant problems with movement if they occur in an important location. Not all tendon injuries are due to lacerations. In some cases, the flexor tendon injury can occur if the tendon end pulls away from bone, if the tendon ruptures due to wear, or if the tendon-muscle interface separates. In the hand, wrist and forearm lacerations are the most common cause of flexor tendon injury. However, if you lose motion in a part of your arm, then tendon injury, even without a laceration, should be considered a possible cause.

Signs and Symptoms

If a tendon is completely ruptured or lacerated, you will not be able to bend part of your arm or hand . This lack of movement can involve just a small area in your hand, or it can be the inability to move multiple joints in the arm. The level of impairment depends on where the injury is located. The flexor tendons in the arm, wrist and hand are in very close proximity to nerves and arteries. It is not unusual to have numbness, tingling and a lot of bleeding after a tendon is lacerated. This is because there can be an injury to these other vital structures as well. These additional injuries are less common in a flexor tendon injury not caused by laceration. For any laceration, it is very wise to see a doctor as soon as you can, particularly if you notice any change in function of the arm.


If you are worried about a flexor tendon injury, please see a hand surgeon right away. It is often easier to treat these injuries early after injury. Flexor tendon injuries do not heal by themselves and frequently require surgery to put the injured tendon back to its normal position. When surgery is required, a splint and hand therapy may be used after the procedure to protect you and to aid in recovery. Typically, any additional injured structures are repaired at the same time as the tendon.


Tendon injuries can result in scarring and stiffness after the surgery. It is not unusual to need additional surgery to improve stiffness. Typically, hand therapy is started after the procedure to aid your recovery. It is important to follow the surgeon’s instructions to avoid re-injury. Many people can have good outcomes after tendon repairs are done, but this is not true in every case. Even in cases where people do well after a flexor tendon injury, the recovery can take many months to complete.



Extensor Tendon Injury

Extensor tendons are just under the skin. They lie next to the bone on the back of the hands and fingers and straighten the wrist, fingers and thumb (Figure 1). They can be injured by a minor cut or jamming a finger, which may cause the thin tendons to rip from their attachment to bone. If not treated, an extensor tendon injury may make it hard to straighten one or more joints.

Common Extensor Tendon Injuries

  • Mallet Finger refers to a drooping end-joint of a finger. This happens when an extensor tendon has been cut or torn from the bone (Figure 2). It is common when a ball or other object strikes the tip of the finger or thumb and forcibly bends it.
  • Boutonnière Deformity describes the bent-down (flexed) position of the middle joint of the finger. Boutonniere can happen from a cut or tear of the extensor tendon (Figure 3).
  • Cuts on the back of the hand can injure the extensor tendons. This can make it difficult to straighten your fingers.
Figure 1
Extensor tendons, located on the back of the hand and fingers, allow you to straighten your fingers and thumb

Figure 2
The mallet finger deformity causes a droop of the fingertip. This is caused by an extensor tendon injury at the last finger joint.

Figure 3
A boutonniere deformity, a type of extensor tendon injury, with progressive bending of the middle joint may result in a stiff finger in this position if not treated. The end joint also bends backward across the finger.


Tears caused by jamming injuries are usually treated with splints. Splints hold the tendon in place and should be worn at all times until the tendon is healed. The tendon may take eight to twelve weeks to heal completely. Longer periods of splinting are sometimes needed. Your doctor will apply the splint in the correct place and give you directions on how long to wear it.

Other treatment for an extensor tendon injury may include stitches (for cuts in the tendon). Also, a pin may need to be placed through the bone across the joint as an internal splint. Surgery to free scar tissue is sometimes helpful in cases of severe motion loss.

After treatment, hand therapy may be necessary to improve motion. Consult your hand specialist for the best form of treatment.

© 2014 American Society for Surgery of the Hand

This content is written, edited and updated by hand surgeon members of the American Society for Surgery of the Hand.


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