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First CMC Joint Bursa

bursa articulationis carpometacarpalis pollicis

A small bursa at the first CMC joint develops in response to arthritic change and joint synovitis at the basal thumb joint. It lies on the dorsal radial surface of the thumb base adjacent to the CMC capsule. The bursa is not normally present but develops in early osteoarthritis as a response to joint inflammation and capsular distension.

Region: Hand & Wrist

Clinical Relevance

Clinical Notes

First CMC bursal swelling is an early clinical sign of basilar thumb arthritis (trapezio-metacarpal arthrosis), appearing as a dorsal radial thumb base prominence (the Eaton-Littler grind test dorsal ballottement) before significant radiographic change. The bursa is often tender on direct palpation. Aspiration and corticosteroid injection into the CMC joint typically addresses both the joint synovitis and the associated bursal inflammation. As arthrosis progresses, the adduction collapse deformity from anterior oblique ligament failure develops.

Pathology

Common Injuries & Conditions

First CMC Bursal Swelling as Early Arthritis Sign

Prominence and tenderness at the dorsal radial thumb CMC base from reactive bursitis is an early clinical sign of basilar thumb arthritis, preceded by the typical pinch pain and followed by the classic adduction deformity; CMC joint corticosteroid injection combined with thumb spica splinting manages early symptomatic disease before surgical intervention is considered.