Abductor Pollicis Longus and Extensor Pollicis: Pain Pattern and Treatment
The abductor pollicis longus and the two thumb extensors run from the back of the forearm to the thumb, their tendons forming the ridges of the anatomical snuffbox at the wrist. They lift the thumb out and back. Their documented pattern is pain at the back of the wrist on the thumb side and along the back of the thumb, from trigger points in the forearm. This is the territory of de Quervain tenosynovitis, and the page tells them apart: the tendon sheath at the wrist is one problem, the muscles above it in the forearm are another, and the splint treats only the first. This is a sub-page of the forearm extensor group page.
Attachments and action
Origin: Abductor pollicis longus: the backs of the ulna and the radius and the interosseous membrane, in the middle of the forearm. Extensor pollicis brevis: the back of the radius and the interosseous membrane below it. Extensor pollicis longus: the back of the ulna and the interosseous membrane.
Insertion: Abductor pollicis longus: the base of the first metacarpal. Extensor pollicis brevis: the base of the proximal phalanx of the thumb. Extensor pollicis longus: the base of the distal phalanx of the thumb.
Action: Abduction and extension of the thumb at the base, the middle joint, and the tip, respectively; together they lift the thumb out of the palm.
Where the pain is felt: At the back of the wrist on the thumb side, at the snuffbox; in a needling study of the abductor pollicis longus this was the site in 62 percent of subjects. Along the back of the thumb from the base toward the tip. Sometimes up the thumb side of the back of the forearm, and in some people on the backs of the middle and ring fingers. Worst lifting the thumb out, texting, and lifting a child under the arms.
Common causes: Texting and scrolling with the thumb; lifting a baby under the arms, the "mother's thumb"; gardening with pruners; wringing; racquet sports; a keyboard with the thumb held out on the space bar; a fall onto the hand.
Patients say: "They said de Quervain and the splint did nothing." "Pain at the back of my wrist by the thumb." "Lifting my baby is the worst." A thumb that aches along the back when I text.
When to get evaluated: Wrist pain after a fall on the hand, with tenderness in the snuffbox itself, needs an X-ray for a scaphoid fracture first, and a repeat film or a scan if the first is normal and the tenderness continues. A wrist that is swollen and creaks over the thumb tendons is tenosynovitis and is treated as such alongside this muscle. Numbness on the back of the thumb needs a nerve assessment.
How this muscle is examined and treated
Examination does the Finkelstein test to grade the tendon sheath, then presses the three muscles on the thumb side of the back of the forearm for the points that reproduce the wrist and thumb pain, and checks the snuffbox for bone tenderness. Needling here addresses the muscles in the back of the forearm, not the tendons at the wrist. Assessment and treatment happen in the same visit.
Related conditions
TendinitisSports & Performance InjuriesChronic Pain Patterns
This page is educational. It describes muscle referral patterns commonly associated with pain; it does not diagnose your condition. Individual patterns vary. For evaluation of your specific pain, see a licensed clinician. Seek immediate medical care for emergencies. Eugene Baek, L.Ac. · New Jersey License 25MZ00080600