is the human opposable thumb a single joint or does it have multiple joints?

The thumb has multiple joints. (three)

The human opposable thumb consists of multiple joints. It has two primary joints: the carpometacarpal (CMC) joint and the metacarpophalangeal (MCP) joint. These joints enable the thumb to move and rotate in different directions, allowing for the characteristic opposable movement. The CMC joint is located at the base of the thumb, where it connects to the wrist, and the MCP joint is in the middle of the thumb, connecting the thumb's metacarpal bone to the proximal phalanx bone. These joints work together to provide the thumb with its flexibility and dexterity.