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Carpometacarpal Joint of the Thumb

articulatio carpometacarpalis pollicis

The carpometacarpal joint of the thumb is a saddle joint that allows the thumb its remarkable opposition ability, the movement that defines fine human hand function. Its two reciprocally curved surfaces allow multiplanar gliding and rotation, making it the most mobile joint in the wrist-hand complex. It is the second most common site of osteoarthritis in the hand after the DIP joints, producing the classic basal thumb arthritis that affects particularly postmenopausal women.

Region: Hand & Wrist

Clinical Relevance

Clinical Notes

Thumb CMC osteoarthritis produces pain at the base of the thumb that worsens with pinching and gripping, positive grind test with axial compression and rotation of the first metacarpal on the trapezium, and eventual squaring of the thenar eminence as the first metacarpal subluxes dorsally. Management progresses from splinting and corticosteroid injection to surgical trapezium excision with or without ligament reconstruction for advanced disease.

Pathology

Common Injuries & Conditions

CMC Thumb Osteoarthritis

Degenerative arthritis at the base of the thumb producing pinch pain, positive grind test, and eventual subluxation, managed with splinting, injection, and surgical trapezium excision in advanced cases.

Bennett Fracture

Intra-articular fracture dislocation of the base of the first metacarpal from an axial loading injury, producing unstable proximal first metacarpal dislocation requiring surgical fixation.