Motion
The carpometacarpal joints of the 2nd to 5th fingers are synovial plane joints. The carpal bones of the wrist articulate with the second to fifth metacarpals. The second metacarpal articulates with the trapezoid primarily and also with the trapezium and capitate. The third metacarpal articulates with the capitate. The fourth metacarpal articulates with the capitate and hamate. The fifth metacarpal articulates with the hamate. They permit flexion, extension, abduction, adduction and circumduction. The mobility of these joints decreases from the fifth to the second CMCs.
Stability
One shared fibrous joint capsule plays an important role in uniting the bones of these joints. The synovial membranes are often a continuation of those surrounding the intercarpal joints.
A number of important ligaments further stabilize the joints:
-Dorsal ligaments
-Palmar ligaments
-Interosseus ligaments.
Muscles
Flexion:
Flexor carpi radialis
Flexor carpi ulnaris
Palmaris longus
Flexor digitorum superficialis
Flexor digitorum profundus
Extension:
Extensor carpi ulnaris
Extensor carpi radialis longus
Extensor carpi radialis brevis
Extensor digitorum
Extensor digiti minimi
Abduction:
Flexor carpi radialis
Extensor carpi radialis longus
Flexor carpi radialis brevis
Adduction:
Flexor carpi ulnaris
Extensor carpi ulnaris
Circumduction:
Sequential action of all carpal flexors and extensors.
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