Opposition is the thumb movement that brings the tip of the thumb in contact with the tip of a finger.
This movement is produced at the first carpometacarpal joint, which is a saddle joint formed between the trapezium carpal bone and the first metacarpal bone. Thumb opposition is produced by a combination of flexion and abduction of the thumb at this joint.
Returning the thumb to its anatomical position next to the index finger is called reposition (Picture 1 l).
