Flexor Tendon Sheath Infections

Flexor tenosynovitis, or a flexor tendon sheath infection, is a serious infection around the tendons of the finger.

With this type of infection, it's important to seek treatment immediately, as delayed care can lead to severe consequences.

Doctor examining patient's hand.

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This article explains what a flexor tendon sheath infection is. It also discusses signs and symptoms, treatment options, and possible complications of this infection.

What Is the Flexor Tendon Sheath?

The flexor tendon is a flexible band of tissue that connects the lower arm muscles to the bones of the fingers and thumb. When the lower arm muscles contract, the fingers are pulled by the flexor tendons into a fist.

The flexor tendons run through a tunnel of tissues called the flexor tendon sheath. The flexor tendon sheath:

  • Allows for smooth gliding of the tendon, which helps with agile finger movement
  • Prevents bowstringing, which occurs when the tendons are pulled in a straight line, which makes certain movement difficult
  • Holds the tendons against the finger, which helps with grasping objects

What Is a Flexor Sheath Infection?

Most often, a flexor sheath infection occurs after an injury to the finger. However, injury to the hand, wrist, or lower arm can also lead to this infection.

Injuries may include a cut, an animal bite, a puncture wound, or a traumatic pulling movement. If bacteria are introduced into the sheath, an infection can develop.

Signs and Symptoms of Infection

The signs of infection usually develop within a week of the injury. Signs and symptoms of an infected flexor tendon sheath include:

  • Swelling of the finger
  • Tenderness along the tendon sheath
  • Limited movement, with the finger held slightly bent
  • Pain when trying to move the finger

These signs are called "Kanavel's cardinal signs," named after the physician who described them. These signs help healthcare providers rule out other similar conditions.


A flexor sheath infection can occur after injury to the finger, hand, wrist, or lower arm. Healthcare providers may use Kanavel's cardinal signs to help diagnose this condition.


Flexor sheath infections should be treated as soon as possible. Some research suggests that individuals who are diagnosed early on may be able to recover within two to 11 days by taking antibiotics given through a vein. In addition to medication, elevating the injured hand and immobilizing it with a brace also help.

In other cases, more aggressive treatment options may be needed. Depending on the severity of the infection, treatment options may include different types of surgery. These may involve:

  • An incision to drain and irrigate, or wash out, the sheath
  • Opening the entire sheath to clean out the infection
  • Oral antibiotics, taken by mouth, after surgery


Flexor sheath infections may take months to a year to fully recovery from. Delayed treatment, smoking, and diabetes have been linked to more severe infections. Immunodeficiency, or when the body isn't able to fight off infections as well as it should, is also associated with more severe infections.

Complications of severe infections include:

  • Decreased blood supply and bone tissue death, as well as bone infection
  • Finger stiffness and decreased range of motion, which may be permanent
  • Finger amputation, which is when the impacted finger must be surgically removed

Individuals may work with hand therapists after their infection has resolved to help recover mobility.


A flexor tendon sheath infection is a serious condition that impacts the area around the tendons of the finger, known as the sheaths. The tendon sheaths help with hand movement.

This infection may develop after injury to the finger, hand, wrist, or lower arm. Typical symptoms are known as Kanavel's cardinal signs. These are used to help diagnose this infection.

Treatment may include antibiotics, as well as surgery depending on the severity of the infection. Complications for this condition can be serious.

A Word From Verywell

An infected flexor tendon sheath is a serious problem that can have long-term repercussions. If you are experiencing any signs or symptoms of this condition, be sure to see your healthcare provider immediately. Doing so offers you the best chance of recovery.

Frequently Asked Questions

  • How serious is a flexor tendon sheath infection?

    A flexor tendon sheath infection is a serious condition that requires immediate treatment.

  • How long does it take to heal from a flexor tendon sheath infection?

    It can take months to a year to recover from a flexor tendon sheath infection.

  • How does a flexor tendon sheath become infected?

    A flexor tendon sheath may become infected after an injury to the finger, hand, wrist, or lower arm. Injuries may include a puncture wound, animal bite, sudden pulling motion, or a deep cut.

8 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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By Jonathan Cluett, MD
Jonathan Cluett, MD, is board-certified in orthopedic surgery. He served as assistant team physician to Chivas USA (Major League Soccer) and the United States men's and women's national soccer teams.