Trigger Finger (Stenosing Tenosynovitis)

Trigger finger, or stenosing tenosynovitis, is catching or locking of a digit caused by stenosis at the A1 pulley.

Who. Prevalence is 2-3% in the general population. Women are affected more often than men (6:1) and incidence peaks at 50-60 years. Middle-aged women are the classic demographic.

Which digit. The thumb and ring finger are the most often affected, then the long finger, with the index and little fingers least often. The percentages below come from the Rozental cohort of 124 digits carded in the Evidence Base. Other series place the ring finger first, so the rank order of thumb and ring is not settled, and the neatly rounded five-digit breakdowns in circulation are not traceable to any cohort.

Multiple digits are commonly involved, especially in diabetes.

Risk factors. Diabetes raises the prevalence to 10%; screen diabetic patients for trigger finger. The other associations:

• Rheumatoid arthritis - inflammatory tenosynovitis
• Gout - crystal-induced
• Repetitive gripping - occupational
• Carpal tunnel - an associated condition

The pulleys. The flexor sheath has five annular pulleys (A1-A5) and three cruciate pulleys (C1-C3). The annular pulleys lie at these levels:

• A1 - MCP joint, where trigger finger occurs
• A2 - over the proximal phalanx
• A3 - PIP joint
• A4 - over the middle phalanx
• A5 - DIP joint

A1 is short and lies at the MCP joint; A2 is long and runs over the proximal phalanx. The junction between them is the boundary of the release.

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The lesion. Repetitive friction thickens the tendon sheath at A1, and a nodule forms in the flexor tendon (FDS or FDP). The nodule catches at the narrowed pulley, producing catching, triggering or locking.

Green's grading runs from pain with only a history of catching, through demonstrable catching and locking that needs passive extension, to a digit that cannot be passively extended. Higher grades are progressively more likely to need surgery.

History. The patient describes catching or clicking during flexion and extension, and locking that may need passive unlocking. Symptoms are worse in the morning, from tissue oedema after rest, and get worse over time. The pain is in the palm over the MCP crease. Ask about diabetes and occupation.

Examination. Palpate at the MCP crease, not the PIP joint: the nodule and the tenderness are over the A1 pulley. Demonstrate the triggering with flexion and extension, grade it by whether the finger extends actively, needs passive extension or is fixed, and check all the other digits.

Differential Diagnosis

The post-traumatic mimic. A digit that catches after an injury and has no A1 nodule warrants a radiograph, because the mechanical catching may be at the bone rather than the pulley.

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Clinical diagnosis. A palpable nodule at A1 with triggering is pathognomonic, and typical trigger finger with clear clinical findings needs no imaging.

Screen for diabetes. Check HbA1c or fasting glucose in a patient not known to be diabetic. Diabetic patients need careful counselling about the lower success of injection.

Ultrasound. Rarely required, and useful when the diagnosis is uncertain. It can show thickening of the tendon sheath and of the A1 pulley, and a tendon nodule. High-resolution ultrasound can measure A1 length and thickness at the metacarpal head and distinguish its distal edge from the A2 pulley. The pathological A1 pulley is thickened and hypoechoic over the FDS and FDP tendons at the MCP joint.

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Atypical lesions. An A1 pulley ganglion may be inconspicuous on long-axis imaging and clear only in short axis, which is why dynamic biplanar ultrasound is useful when the palpable lesion is atypical. A discrete calcific focus superficial to A1, separate from the sesamoid and with adjacent Doppler signal, is a rare structural cause that can mimic ordinary stenosing tenosynovitis.

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These are the complications to consent for.

• Subcutaneous fat atrophy and skin hypopigmentation at the injection site. Steroid that tracks into the dermis or subcutaneous fat leaves a depressed, pale patch that is cosmetically distressing, often slow to recover or permanent, and more conspicuous in darker skin. Warn patients, and keep the injection deep to the dermis, in the sheath.
• Transient hyperglycaemia in diabetics. A single injection can raise blood glucose for several days, which matters both for consent and for the inject-or-operate-first debate in diabetes.
• Flexor tendon attenuation or rupture. Rare, but it is the reason the steroid goes into the sheath and not the tendon, and the reason to limit the number of injections: repeated intratendinous steroid weakens the tendon.
• Steroid flare - a short-lived increase in pain in the first 24-48 hours is common.
• Infection - rare with aseptic technique.

Bowstringing. A2 pulley injury causing bowstringing is a serious complication, and knowing the anatomy is the prevention. The bowstringing measured on ultrasound after A1 release alone is a different finding: in Park's trial it increased at 12 weeks after both open and percutaneous release, resolved by 24 weeks and was not associated with any clinical outcome.

When a finger is still troublesome after release, first separate two different problems, because they have different solutions.

Why WALANT. Operating wide awake lets the patient actively flex and extend on the table, so residual triggering from an FDS nodule is caught and dealt with at the index operation rather than discovered at the post-operative review. The answer to persistent triggering is to address the A1 release and the FDS, never to divide the A2 pulley.

Return to work. Light duties immediately, and full duties at 2-4 weeks.

Success rates. Splinting alone gives variable results (30-40%). Injection succeeds at the rates given under Management, and surgery in 95-100%.

After injection specifically. In the Rozental cohort, duration and severity of symptoms did not predict the outcome of injection; insulin-dependent diabetes, younger age, multiple digits and other upper-limb tendinopathies did.

Most patients do very well with injection or surgery.

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Global epidemiology: Lifetime prevalence is approximately 2-3% in the general population, rising to 5-20% in people with diabetes. Peak onset is in the fifth-to-sixth decade, with a female predominance (roughly 2-6:1 across series). Trigger finger is one of the commonest reasons for elective hand surgery worldwide and is a recognised marker of impaired glucose tolerance.

Side-by-side guidance:

Related pages: Trigger Thumb covers the paediatric entity, which is a different disease despite the shared name - Notta's node, frequent spontaneous resolution, and no role for injection; De Quervain Tenosynovitis is the other stenosing tenosynovitis of the hand and shares the injection-first algorithm and the same weak evidence base; Dupuytren Disease is the principal differential for a palmar nodule and coexists often enough that both should be examined for at every visit; Flexor Tenosynovitis is the infective mimic - Kanavel's signs and pain on passive extension distinguish it, and mistaking it for a trigger digit is the dangerous error on this page; Flexor Tendon Repair Techniques and Flexor Tendon Rehabilitation hold the pulley anatomy and the bowstringing consequences that make A2 preservation non-negotiable, and Flexor Tendon Lacerations covers the partial laceration that can catch without a nodule; Carpal Tunnel Syndrome coexists with trigger finger frequently and shares diabetes as a driver; and Ganglion Cysts include the flexor sheath (seed) ganglion, a tender palmar lump at the A1 pulley that does not trigger.

How many injections before surgery. Most surgeons offer one or two injections before recommending release, but the optimal ceiling is debated. Recurrence is around 56% at one year (Rozental 2008), and repeated injections of diminishing benefit carry cumulative cost and complication risk, so most clinicians proceed to release after one or two failed injections, sooner in high-risk patients (insulin-dependent diabetes, multiple digits, young age). Yet in that same cohort only 18% actually came to surgery, and freedom from surgical release was 83% at twelve months.

Recurrence is therefore not the same as failure: most recurrences were tolerated or re-injected. Both figures belong in the discussion, because the first argues for operating sooner and the second argues that most patients never need to.

Open or percutaneous release. Randomised data show equivalent clinical outcomes for open and percutaneous (including ultrasound-guided) release. The choice is largely dependent on operator expertise.

Ultrasound guidance for injection. It improves accuracy and may speed early recovery, but several trials show no difference in 3-6 month outcomes against a blind landmark-based injection. Routine use is not yet standard and depends on availability.

Diabetics: inject or operate first? Whether to attempt injection at all in insulin-dependent diabetic patients, given the transient glycaemic disturbance and low success, remains a point of practice variation.