The carpometacarpal joint (CMC joint) is a critical joint located in the hand, connecting the carpal bones of the wrist to the metacarpal bones of the fingers. This joint allows for a range of movements, including flexion, extension, abduction, and adduction, which are essential for hand function. The most notable CMC joint is the one at the base of the thumb, known as the first carpometacarpal joint. This joint is unique because it allows for opposition, enabling the thumb to touch the other fingers, which is vital for grasping and manipulating objects effectively.