• Origin

Posterior surface of the middle third of the ulna.
Interosseous membrane (adjacent part).

• Insertion

Base of the distal phalanx of the thumb (dorsal aspect).

• Agonist(s)

- Extensor pollicis brevis (synergist in thumb extension),

- Abductor pollicis longus (aids in thumb abduction and extension),

- Extensor indicis (synergist in extension of the hand).

• Antagonist(s)

- Flexor pollicis longus,

- Flexor pollicis brevis,

- Adductor pollicis.

• Function

Extends the thumb at the interphalangeal joint.
Assists in extending the thumb at the metacarpophalangeal and carpometacarpal joints.
Assists in radial deviation and extension of the wrist.

TRIGGER POINT(S)

• Location

Trigger points for both muscles are typically found along the posterior-lateral forearm, especially in the middle to distal third of the forearm, near the bony structures of the radius and ulna.

• Pain Referral Pattern

Pain can refer to the lateral side of the wrist and into the thumb, especially on the dorsal surface.

It may mimic symptoms of De Quervain’s tenosynovitis or lateral wrist pain during gripping motions.

💢

Potential Causes

• Repetitive thumb or wrist extension (e.g., texting, typing, gaming, playing instruments).

• Chronic overuse of the thumb in gripping, lifting, or pinching tasks.

• Inflammation of the tendons as they pass through the first dorsal compartment.

• Poor ergonomics during frequent hand and wrist activity.

• Muscle imbalance or weakness in opposing thumb flexors.

✅

Prevention Tips

• Limit repetitive thumb use and take regular breaks during prolonged activity.

• Use ergonomic tools and wrist supports during typing or gaming.

• Perform regular thumb and wrist stretches and strengthening exercises.

• Apply proper grip techniques when lifting objects or using tools.

• Warm up and mobilize wrist/thumb before physical activities involving the hand.