✋ De Quervain's Tenosynovitis Finkelstein Test Simulator

The First Dorsal Compartment — A Tight Tunnel for Two Tendons

Two thumb tendons share one narrow fibro-osseous tunnel at the wrist.

• 2: Compartment tendons (APL and EPB)
• ~1 mm: Normal sheath thickness (thin synovial lining)
• Radial styloid: Location (first dorsal compartment)
• Thumb abduction: Function (and extension)

Two tendons, one tunnel

Abductor pollicis longus and extensor pollicis brevis share this compartment.

A thin synovial sheath lets both tendons glide smoothly under the retinaculum.

Up to a third of people even have a septum splitting the tunnel.

Why the tunnel is vulnerable

The compartment sits directly over the radial styloid, a bony pulley point.

Every thumb movement forces tendons to angle sharply around this bone.

That friction point is exactly where inflammation later concentrates.

Gliding mechanics

A healthy sheath secretes synovial fluid, keeping friction near zero.

Tendons slide several millimeters with each thumb motion, unimpeded.

Named for Fritz de Quervain, who first described this condition in 1895.

Repetitive Thumb Use — Microtrauma Accumulates in the Sheath

Repeated gripping, texting, and lifting overload the tendon-sheath interface.

• Texting, lifting: Common triggers (new-parent wrist-carrying)
• 6:1: Sex ratio (women more affected)
• 30–50: Peak age range (years old)
• Gradual: Onset (weeks of overuse)

Friction builds with repetition

Repeated ulnar-radial thumb motion grinds tendons against the retinaculum.

Microtears accumulate faster than the sheath can repair them.

Common real-world causes

Texting thumbs, racquet sports, knitting, and lifting a baby all contribute.

New parents get this so often it is nicknamed "mommy thumb".

Early warning signs

A dull ache at the wrist base appears first, worsened by grip.

Swelling is often still too subtle to see.

Occupations with repetitive grasping show markedly higher De Quervain incidence.

Tenosynovitis Develops — Sheath Thickening Narrows the Compartment

Chronic irritation thickens the sheath, squeezing both tendons inside.

• 2–5 mm: Sheath thickness (up from ~1 mm)
• Fibrosis: Tissue change (myxoid degeneration)
• Tender nodule: Palpable finding (over radial styloid)
• Up to 70%: Compartment narrowing (space for tendons)

Thickening mechanism

Chronic friction triggers fibroblast proliferation and collagen deposition.

The sheath wall thickens, and the tunnel effectively shrinks around the tendons.

Stenosing tenosynovitis

The condition is technically a stenosing process, not true infection or tear.

Tendons themselves stay intact but glide with visible resistance.

Palpable changes

A firm, tender swelling becomes palpable directly over the styloid.

Grip strength and thumb range of motion both decline.

Swelling can be visible as a firm bump before any test is performed.

Finkelstein Test — Ulnar Deviation Compresses the Inflamed Sheath

Tucking the thumb into a fist and deviating ulnarly reproduces sharp pain.

• Thumb tuck: Test maneuver (+ ulnar deviation)
• ~81%: Sensitivity (clinical studies)
• ~50–98%: Specificity (varies by study)
• Radial styloid: Pain location (sharp, localized)

How the test works

The patient makes a fist around the tucked thumb, then bends the wrist toward the pinky.

This stretches the inflamed tendons tightly across the swollen sheath.

Why it hurts

Ulnar deviation maximizes tension exactly where the sheath is thickest.

Compressed, inflamed tissue fires nociceptors, producing sharp radial-side pain.

Interpreting a positive test

Sharp pain at the radial styloid confirms the clinical diagnosis.

Imaging is rarely needed when the test is clearly positive.

A positive Finkelstein test alone is usually enough to diagnose De Quervain's.

Splinting and Corticosteroid Injection Reduce Sheath Inflammation

A thumb spica splint rests the tendons; injection targets inflammation directly.

• ~70%: Splint success rate (mild-moderate cases)
• ~80–90%: Injection success rate (single corticosteroid shot)
• 4–6 weeks: Splint duration (typical course)
• <10%: Surgery need (refractory cases only)

Thumb spica splinting

Immobilizing the thumb and wrist rests the tendons and lets swelling settle.

Worn several weeks, it is the first-line conservative treatment.

Corticosteroid injection

A steroid injected into the sheath directly suppresses local inflammation.

Most patients feel significant relief within one to two weeks.

When surgery is considered

Release of the compartment roof is reserved for refractory cases.

Most patients never need to escalate beyond splint and injection.

Combining splint and injection outperforms either treatment used alone.