Merck Manual

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Infection of the Tendon Sheath in the Fingers

(Infectious Flexor Tenosynovitis)


David R. Steinberg

, MD, Perelman School of Medicine at the University of Pennsylvania

Reviewed/Revised Apr 2022 | Modified Sep 2022
Topic Resources

A bacterial infection can develop in the tendon sheath that surrounds the tendons in the palm and inside of the fingers.

Pockets of pus (abscesses) may occur around the tendons Tendons and Bursae Tendons are tough bands of connective tissue made up mostly of a rigid protein called collagen. Tendons firmly attach each end of a muscle to a bone. They are often located within sheaths, which... read more that run along the inside of the hand and fingers. These tendons are inside a sleeve of tissue called the tendon sheath. The sheath helps the tendons slide smoothly.

A tendon sheath abscess is caused by an injury that penetrates one of the creases on the palm side of a finger. Pus from an untreated felon Felon A felon is an infection of the soft tissue (pulp) of the fingertip, usually caused by bacteria. A felon can lead to a pocket of pus (abscess) inside the fingertip, which creates pressure on... read more Felon may also spread from the tip of the finger into the end of the tendon sheath. Infection and pus form around the tendon and rapidly destroy tissue. The gliding mechanism of the tendon becomes damaged, so the finger can barely move.

Symptoms of infection of the tendon sheath include swelling and pain of the finger and tenderness over the tendon sheath. The finger feels better when it is bent (flexed). Moving the finger can cause extreme pain. Fever is common.

Diagnosis of a Tendon Sheath Infection

  • A doctor's examination

  • X-rays

  • Cultures

Doctors base the diagnosis of infection of the tendon sheath on an examination. They do x-rays X-rays A doctor can often diagnose a musculoskeletal disorder based on the history and the results of a physical examination. Laboratory tests, imaging tests, or other diagnostic procedures are sometimes... read more X-rays to detect foreign bodies (such as a tooth fragment, needle, or other object) that may be hidden under the skin.

To identify the type of bacteria that is causing the infection, doctors remove a sample of pus from the abscess and try to grow (culture Culture of Microorganisms Infectious diseases are caused by microorganisms, such as bacteria, viruses, fungi, and parasites. Doctors suspect an infection based on the person's symptoms, physical examination results,... read more ) the bacteria in a laboratory.

Treatment of a Tendon Sheath Infection

  • Drainage of pus

  • Antibiotics

The person is admitted to the hospital. Doctors drain the pus through a surgical incision. Antibiotics are given by vein (intravenously).

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