What characterizes a saddle joint?

A saddle joint is characterized by the way its two articulating surfaces are shaped, specifically with one bone having a concave region and the other having a convex region. This unique configuration allows the bones to fit together in a way that enables significant movement in multiple directions, including flexion, extension, abduction, and adduction. An excellent example of a saddle joint in the human body is the carpometacarpal joint of the thumb, which allows for a greater range of motion compared to other joint types.

The design of a saddle joint promotes versatility and stability, differentiating it from other joint types. For instance, in a hinge joint, movement is restricted primarily to one plane (flexion and extension), while ball-and-socket joints permit rotation as well. By allowing both flexion and extension as well as adduction and abduction, saddle joints play a critical role in the dexterity needed for specific tasks, such as grasping or gripping objects.