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The flexor tendons allow you to bend your fingers.

Tendons are strong cords that connect muscles to bone. When muscles contract, their tendon(s) pull through the attachments to bone and cause a joint to move. 

The muscles that move the fingers and thumb are located in the forearm and hand. Long tendons run from the end of the muscles through small tunnels in the wrist and hand to attach to the small bones (phalanges) of the fingers and thumb. These tunnels are called tendon sheaths. The tendon sheaths keep the tendons close to the bones and joints and also provide lubrication to the tendons to help them glide freely.

Tendon sheaths keep the tendons in place.

A cut or ruptured tendon in the forearm, at the wrist, in the palm, or along the finger will make it difficult or maybe impossible to bend one or more joints in a finger.

Like a rubber band, the flexor tendons are under tension as they connect the muscle to the bone. If a tendon is torn or cut, the ends of the tendon likely will be pulled apart, making it impossible for the tendon to heal on its own because of the gap between the two ends.

It is not uncommon for other structures to be injured at the time of a cut flexor tendon. Because the nerves and blood vessels to the fingers are very close to the tendons, a cut may damage them, as well. This can cause numbness on one or both sides of the finger. If blood vessels are also cut, the finger may have no blood supply, which can cause loss of the finger. This requires immediate surgery.

Occasionally, flexor tendons may be partially cut or torn. With a partial tendon injury, it may still be possible to bend your finger. However, partial tendon injuries may result in incomplete bending of the finger, excessive pain, or even catching or locking of the finger during movement. Partial injuries to the tendons can be difficult to diagnose.

In addition to cuts on the arm, wrist, hand, or fingers, certain sports activities can cause flexor tendon injuries. These injuries often occur in football, wrestling, and rugby. Jersey finger is one of the most common of these sports injuries. It can happen when one player grabs another's jersey and a finger (usually the ring finger) gets caught and pulled with great force. This can cause the tendon to be pulled off the bone.

In activities that require a lot of a hand strength (e.g., rock climbing), tendons and/or their sheaths can also be stretched or torn. The crimp-grip position of the fingers necessary for rock climbing places a great deal of strain on the pulleys of the tendon sheath and can cause a rupture of the sheath. When this occurs, it can limit how much the finger can bend  or flex and can cause pain when moving the finger.

Certain health conditions (rheumatoid arthritis, for example) weaken the flexor tendons and make them more likely to tear or rupture. This can happen without warning or injury — a person may simply notice that their  finger no longer bends but not recall how it happened.

The most common signs of a flexor tendon injury include:

• An open injury, such as a cut, on the palm side of your hand, wrist, or forearm
• An inability to bend one or more joints of your finger
• Pain when you attempt to bend your finger
• Tenderness along your finger on the palm side of your hand
• Numbness in your fingertip

It is important to see a doctor whenever the fingers are injured. This is especially true for an open injury or cut in the skin, and when you are concerned that you might have a tendon injury. Generally, it is recommended that flexor tendon injuries should be repaired within 7 to 10 days of the injury, although early evaluation is important.

Physical Examination

During the examination, your doctor will ask you to bend and straighten your fingers. To test your finger strength, your doctor may have you try to bend your injured finger while they hold the other fingers down flat. To determine whether any nerves or blood vessels have been injured, your doctor may test your hand for sensation and blood flow to the fingers.

These standard examination tests help your doctor determine if a tendon or nerve has been injured.

Your hand may be placed in a splint for protection prior to surgery.

After examining your hand, your doctor may clean your open wound(s) and close the wound(s) to reduce the risk of infection. They may place your hand in a splint to protect the injured structures.

Tendons cannot heal unless the ends are touching. In most cases, a cut or torn tendon must be repaired by a surgeon. 

Surgery is usually performed within 7 to 10 days after an injury. In general, the sooner surgery is performed, the better recovery will be.

If your injury is restricting blood flow to your hand or finger, your doctor will schedule an immediate surgery. If you are concerned that your finger may need immediate attention, do not eat or drink anything, as this may delay surgery. Go immediately to an emergency room.

Surgical Procedure

Because tendons tear in different ways — such as straight across, at an angle, or pulled right off of the bone — there are many different methods for your surgeon to repair them. Most, if not all of the methods for repair, however, involve special sutures, or stitches.

Your fingers and wrist may be place din a bent position to keep tension off the repair.

Often, depending on your injury, your surgeon will refer you to a hand therapist for several days after your surgery to begin surgical exercises that protect the tendon repair but encourage the tendons to move or glide within the tendon sheath.

It is important that you follow the instructions of your surgeon and your therapist to avoid damaging the tendon repair. The outcome of the repair will depend greatly on your ability to follow the instructions of your surgeon and therapist. 

After surgery, a splint is applied to limit movement and help the tendon heal.

Over the last several decades, advanced research and experience in the treatment of flexor tendon injuries have resulted in improved patient outcomes. Flexor tendon injuries, however, can be very challenging to treat. Even in the best of hands, some patients develop stiffness and poor function of a digit after flexor tendon injury and repair. For this reason, it is very important to be seen promptly if you are concerned you may have a flexor tendon injury. It is also essential to work with therapy and follow all instructions after you undergo a flexor tendon repair to optimize your outcome.

Overall, despite its challenges, flexor tendon surgery results in good return of function and high patient satisfaction for many patients.