What to Know About Hand Extensor Tendon Injuries

Medically Reviewed by Mahammad Juber, MD on October 06, 2022
4 min read

Few creatures on earth have hands like humans do. Human hands are incredible. They’re capable of creating art, building things, playing instruments, and so much more.

Like the rest of your body, your hands are made up of bones, muscles, tissues, and tendons, all working together to allow your hands to function properly. Damage to any of these components can cause issues within your hands. The tendons within your hands are called extensor tendons and are easily damaged, which can result in pain and mobility issues.

Tendons are flexible cords or tissue that connect bones and muscles. Without them, you wouldn’t be able to move your limbs, fingers, or toes.

The extensor tendons are the tendons that run from your forearm up through your fingertips on the back of your hand. These tendons are located between the bones and the skin of the hands and fingers. As a result, these tendons are not well-protected and are prone to injury.

There are several common types of extensor tendon injuries:

  • Mallet Finger is the term for when the end joint of the finger droops. It happens when the finger is jammed and the tendon of that finger ruptures at the base of the finger joint.
  • Boutonnière Deformity is the term describing the middle joint of the finger being bent. It’s often due to a cut or tear to the tendon.
  • Extensor tendonitis refers to inflammation or irritation of the extensor tendons. It can be caused by overwork or repetitive motion.

To help diagnose and treat extensor tendon injuries, doctors have separated the hand into eight extensor tendon injury zones:

  • Zone I consists of the area below the nail through the top finger joint, called the distal interphalangeal joint. This is where mallet finger injuries happen.
  • Zone II is the middle phalanx, the area between the top and middle joint.
  • Zone III covers the middle joint, called the proximal interphalangeal joint. This is where Boutonnière injuries happen.
  • Zone IV consists of the proximal phalanx, the space between the middle joint and the joint that connects the fingers to the hand.
  • Zone V covers the metacarpophalangeal joints, the joints where the fingers meet the rest of the hand.
  • Zone VI consists of everything between the metacarpophalangeal joints and the wrist.
  • Zone VII covers the wrist and the extensor retinaculum. The extensor retinaculum is a band of ligaments that holds the extensor tendons in place.
  • Zone VIII is made up of the forearm ligaments that connect to the hand.

There are many causes of extensor tendon injuries. Those who work with their hands or participate in certain activities may find themselves more prone to extensor tendon injuries.

Jammed fingers. Jammed fingers happen when the tip of the finger is forcefully pushed back towards the hand. This can lead to stretched or sprained ligaments. In severe cases, the ligaments may tear.

Many things can cause jammed fingers. Situations like catching a ball wrong or trying to catch yourself when you fall can result in the tip of the fingers being jammed. Mallet finger is caused by a jammed finger.

Cuts. The extensor tendons are located just underneath the skin. Even mild cuts can cause a disruption in the way they work. Many types of accidents can cause a cut to the back of the hand that slices into the tendon.

Extensor Tendonitis. Inflamed or irritated extensor tendons may lead to extensor tendonitis. Tendonitis is common, especially in those with autoimmune disorders or arthritis. It’s caused by overuse or repetitive motions and can happen in both the hands and feet.

Common activities that may result in extensor tendonitis in the hands include:

  • Cleaning
  • Gardening
  • Painting and art
  • Some sports
  • Typing
  • Woodworking

Most extensor tendon injuries will result in pain and difficulty moving the finger, but other symptoms may vary depending on the type of injury and cause of the injury.

Jammed fingers and mallet finger injuries. Jammed fingers and mallet fingers may have the following symptoms: 

  • Pain
  • Swelling
  • Inability to bend or straighten the injured finger
  • Drooping of the end joint in the injured finger

Boutonniere deformity. Boutonniere deformity often results in symptoms such as:

  • Pain
  • Swelling
  • An inability to straighten the middle joint of the finger
  • An inability to bend the fingertip

Extensor tendonitis. The symptoms of extensor tendonitis include:

  • Pain
  • Swelling
  • Stiffness
  • Discoloration
  • Warmth around the injured tendon

The steps needed to diagnose and treat an extensor tendon injury will depend on the type of injury and the cause of the injury.

In some cases, a physical exam is enough for your doctor to diagnose you. In other cases, your doctor may request an imaging test to confirm their diagnosis or to determine the severity of your injury. These tests may include:

  • X-rays: X-rays use radiation to take pictures of bones and soft tissue. Your doctor would use them to rule out broken bones or dislocations that can happen with some extensor tendon injuries.
  • Musculoskeletal ultrasound: Ultrasounds use sound waves to produce images. They’re able to see soft tissues such as tendons as they move.
  • CT scan: CT scans use X-rays to get a 360-degree view of areas of your body. Your doctor may use this to look for fractures.
  • MRI: MRIs use radio waves and a magnet to produce detailed images of the inside of the body. Your doctor can use this to check for inflammation or see small tears in the tendons.

After diagnosis, your doctor will go over treatment options with you. 

  • Jammed fingers and mallet fingers may be treatable with a splint or “buddy taping,” the method of taping the injured finger to a non-injured one for stability. Severe cases may need surgery.
  • Cuts and lacerations may need stitches.
  • Extensor tendonitis may be treated by resting, icing, compressing, and elevating the injured hand. If that doesn’t work, your doctor may look into providing you with corticosteroid injections.

Your doctor may recommend physical therapy to help your injured hand or finger recover. In some cases, surgery may be needed to reduce or manage scar tissue.