Trigger finger is a painful condition that causes the fingers or thumb to catch or lock when bent. It happens when tendons in the finger or thumb become inflamed.

A tendon usually glides easily through the tissue that covers it (called sheath) because of a lubricating membrane surrounding the joint called the synovium. Sometimes a tendon may become inflamed and swollen.

Prolonged irritation of the tendon sheath can produce scarring and thickening that impede the tendon's motion. When this happens, bending the finger or thumb can pull the inflamed tendon through a narrowed tendon sheath, making it snap or  pop.

trigger finger

Causes
Trigger finger can be caused by a repeated movement or forceful use of the finger or thumb. Rheumatoid arthritis, gout, and diabetes also can cause trigger finger. So can grasping something, such as a power tool, with a firm grip for a long time.

Diagnosis
Trigger finger is diagnosed with a physical exam of the hand and fingers. In some cases, the finger may be swollen and there may be a bump over the joint in the palm of the hand. The finger also may be locked in bent position, or it may be stiff and painful. No X-rays or lab tests are used to diagnose trigger finger.

Classification (grading)

  • Grade I (Pretriggering): There is complaint of pain and history of catching. Catching may not be always present and may not be demonstrable on clinical examination. There is tenderness over the A1 pulley
  • Grade II (Active): Catching can be demonstrated on clinical examination but patient is able to extend the digit actively.
  • Grade III (Passive): IIIa – Demonstrable locking in which passive extension is required
    IIIb – Inability to actively flex the finger
  • Grade IV (Contracture): There is a demonstrable catching, with a fixed flexion contracture of the proximal interphalangeal joint

Treatment

  • Medication
  • Rest, Splinting
  • Corticosteroid injections (into the sheath, not the tendon)
  • Surgical release of A1 pulley. It is performed under local or regional anaesthetic as a day case.

Video

Locking of ring finger during flexion Full flexion - extension after release
 

* Patient consent was obtained for publication of figures