• Origin

Posterior surface of the middle third of the radius.
Interosseous membrane (between radius and ulna).

• Insertion

Base of the first metacarpal (lateral aspect)
Occasionally attaches to the trapezium

• Agonist(s)

- Abductor pollicis brevis,

- Extensor pollicis brevis,

- Opponens pollicis (assists in positioning for abduction).

• Antagonist(s)

- Adductor pollicis,

- Flexor pollicis brevis,

- Flexor pollicis longus (depending on the movement being opposed).

• Function

Abducts the thumb at the carpometacarpal joint.

Assists in thumb extension.

Contributes to radial deviation and extension of the wrist.

Stabilizes the thumb during pinching and gripping.

TRIGGER POINT(S)

• Location

Trigger points are typically located in the proximal to mid-posterolateral forearm, often just distal to the lateral epicondyle of the humerus and along the lateral border of the ulna and radius.

• Pain Referral Pattern

Pain often refers along the lateral wrist and into the base of the thumb.

May radiate into the thenar eminence and mimic symptoms of De Quervain’s tenosynovitis.

Discomfort may be felt when abducting or extending the thumb.

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Potential Causes

• Repetitive gripping, pinching, or thumb abduction (e.g., using a smartphone, tools, or gaming controllers).
• Excessive typing or texting with poor wrist positioning.
• Overuse in racket sports, climbing, or weight training.
• Tight or overworked wrist and thumb extensors compensating for weak flexors.
• Poor ergonomic setup at work or during repeated manual tasks.

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Prevention Tips

• Take frequent breaks from repetitive thumb and wrist activities.

• Strengthen both flexors and extensors of the thumb to avoid imbalance.

• Use ergonomic devices that reduce thumb strain.

• Stretch the thumb, wrist, and forearm regularly.

• Apply proper technique and hand positioning during tool use or lifting.

• Warm up adequately before sports or manual work involving the hand.