The thumb is rotated 90 degrees to the other digits. Thus, abduction and adduction occur in a sagittal plane and flexion and extension occur in a coronal plane. Opposition, the action bringing the tip of the thumb in contact with the pads of the other fingers, is the most complex movement. The components of opposition are abduction and medial rotation at the carpometacarpal joint and flexion of the metacarpophalangeal joint.
Reproduced with permission from: Moore KL, Dalley AR. Clinically Oriented Anatomy, 5th ed, Lippincott Williams & Wilkins, Philadelphia 2006. Copyright © 2006 Lippincott Williams & Wilkins.
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