The carpometacarpal joint of the thumb is more complex than the other carpometacarpal joints. It is a synovial saddle joint and like all saddle joints it is biaxial, but owing to the incongruity of the articulating surfaces, the curvatures of one of the surfaces being always more pronounced than those of the other, the movements about the two axes may be so combined that actual circumduction is possible. The chief movements of this joint are abduction (away from the index-finger perpendicular to the plane of the palm), adduction (toward the index-finger perpendicular to the plane of the palm), extension (away from the index-finger in the plane of the palm), flexion (toward the index-finger in the plane of the palm), and opposition (swinging the metacarpal bone of the thumb in an arching fashion toward the little finger). During the latter motion the concavity of the palm is markedly increased.

Articulatio carpometacarpalis pollicis

Articulation carpométacarpienne du pouce