Trigger thumb

Last revised by Henry Knipe on 7 Sep 2022

Trigger thumb or flexor pollicis longus (FPL) stenosing tenosynovitis is a specific type of trigger finger involving the thumb.

Clinical presentation

Trigger thumb may present as a transient locking of the thumb during flexion, followed by a painful snapping sensation during extension.

Radiographic features


Ultrasound can both show varying degrees of A1 pulley thickening and flexor pollicis longus tendinosis/tenosynovitis. Local swelling of the flexor tendons distal to the pulley may lead to a distinct nodule 2,4. Small cysts may be present at the pulley boundaries due to fluid trapping 5.

Dynamic scanning during passive flexion and extension typically demonstrates difficult tendon gliding underneath the abnormal pulley. Doppler imaging may depict hypervascularity in the region of the pulley and surrounding soft tissues 6,7.


Findings are similar to ultrasound, namely flexor pollicis longus tendinosis/tenosynovitis with a distinct nodule and A1 pulley thickening 2.

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Cases and figures

  • Case 1
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  • Case 2
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  • Case 4
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  • Case 5
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  • Case 6
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  • Case 7: on MRI
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