Trigger finger !

Trigger finger is when a finger's flexor tendon catches on a thickened pulley at its base, so the finger clicks, locks bent or snaps straight.

Updated 2026-10-29

Structures involved

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What it is

Stenosing tenosynovitis in which a flexor tendon catches at a thickened A1 pulley at the base of the finger, so the finger clicks, locks in flexion or snaps straight.

Who gets it

One of the most common hand problems in adults, more frequent in women in their 50s and 60s, and much more common in people with diabetes. The ring finger and thumb are affected most often.

Causes

Thickening and narrowing of the A1 pulley at the metacarpal head
Nodular swelling of the flexor tendon
Repetitive gripping and local mechanical stress
Associated systemic disease

Risk factors

Diabetes mellitus
Rheumatoid arthritis and other inflammatory arthritis
Carpal tunnel syndrome and De Quervain tenosynovitis
Female sex and age 40 to 60 years
Hypothyroidism, gout and amyloidosis
Occupations with repetitive forceful gripping

Pathophysiology

The A1 pulley sits over the metacarpophalangeal joint. Repeated friction causes fibrocartilaginous change in the pulley and a nodule or swelling in the tendon. The mismatch makes the tendon catch as it glides, then pass with a snap, and later lock the finger in flexion.

Classification

Green (modified Quinnell): grade I pain or tenderness at A1 without catching
Grade II catching, but the finger still extends actively
Grade III locking that needs passive extension, or inability to flex fully
Grade IV fixed flexion contracture

Symptoms and signs

Painful click or catching when bending or straightening the finger
Finger locked in flexion, released with a snap, worse in the morning
Tender palpable nodule at the distal palmar crease over the A1 pulley
Pain at the base of the finger or thumb
Stiffness or flexion contracture in long-standing cases

Diagnosis

Clinical: Clinical diagnosis: tenderness and a nodule over the A1 pulley, with catching or locking reproduced on active flexion and extension.
Tests: Blood glucose or HbA1c may be checked when diabetes is suspected; otherwise no tests are needed.
Imaging: Usually unnecessary; ultrasound can show the thickened pulley and tendon, and X-rays help if arthritis or another cause is suspected.

Differential diagnosis

Dupuytren contracture
Ganglion of the flexor tendon sheath
Metacarpophalangeal joint locking or arthritis
Flexor tendon injury
De Quervain tenosynovitis (for thumb pain)

Goal of treatment

Abolish catching and locking, relieve pain, and restore full, smooth finger motion.

Treatment

Conservative: Activity modification and splinting of the affected joint to rest the tendon, mainly in mild cases.
Medical: Non-steroidal anti-inflammatory drugs for short-term pain relief.
Procedure: Corticosteroid injection into the flexor tendon sheath at the A1 pulley; first-line for most patients, though less effective and more often repeated in diabetes.
Surgical: Release of the A1 pulley, open or percutaneous, when injections fail or the finger stays locked; the A2 pulley is preserved.

Complications

Recurrence after injection
Tendon bowstringing if the A2 pulley is injured
Digital nerve injury, especially at the thumb
Persistent stiffness or flexion contracture
Infection or skin changes after injection

Prognosis

Many cases settle with one or more steroid injections. Surgical release has a high success rate and low recurrence; results are less favourable in diabetes and in long-standing contractures.

Test yourself

Think of the answer, then tap the question to see it.

Which pulley is involved in trigger finger?

The A1 pulley, at the level of the metacarpophalangeal joint.

Which systemic disease is most strongly associated with trigger finger?

Diabetes mellitus; rheumatoid arthritis and hypothyroidism are also associated.

What is the usual first-line procedure for trigger finger?

A corticosteroid injection into the flexor tendon sheath at the A1 pulley.

Which pulley must be preserved during trigger finger release, and why?

The A2 pulley, to prevent bowstringing of the flexor tendons.

Which digits are most commonly affected by trigger finger?

The ring finger and the thumb.

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Educational information, not medical advice. For any symptom, see a health professional.

Sources: Trigger Finger (StatPearls (NCBI Bookshelf), 2024).

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Representative model, for educational purposes only.

A1 pulleys highlighted on the Durgical 3D model