Carpalmetacarpal

Carpalmetacarpal refers to the joints between the carpal bones of the wrist and the bases of the metacarpal bones in the hand. In common anatomical usage, it describes the carpometacarpal joints (CMC joints), of which there are five—one for each finger.

The first carpometacarpal joint, between the trapezium and the base of the first metacarpal, forms a saddle joint that allows a wide range of motion, including flexion, extension, abduction, adduction, and opposition. This mobility is essential for thumb opposition and precision grip. The second (trapezoid–second metacarpal) and third (capitate–third metacarpal) joints are relatively rigid, stabilized by strong ligamentous attachments, and provide stability for the hand. The fourth (hamate–fourth metacarpal) and fifth (hamate–fifth metacarpal) joints are more mobile, contributing to the cupping of the hand and facilitating power grip.

Ligamentous support includes the palmar and dorsal carpometacarpal ligaments and the intermetacarpal ligaments that connect adjacent metacarpals. Sensory innervation arises from nerves supplying the hand, corresponding to the regional distribution of the radial, median, and ulnar nerves.

Clinical relevance includes osteoarthritis at the carpometacarpal joints, most notably the first CMC joint, which can cause basal thumb pain and impaired grip. Traumatic injuries may involve fractures at the base of the first metacarpal (such as Bennett’s fracture) or dislocations at other CMC joints. Evaluation typically involves radiographs, with MRI or CT used for complex injuries.