A saddle joint is a type of synovial joint that allows movement in two planes, providing greater flexibility than a hinge joint. It is characterized by two bone surfaces that fit together like a rider in a saddle, with one surface being concave and the other convex. This unique shape enables a range of motions, including flexion, extension, abduction, and adduction. One of the most well-known examples of a saddle joint is the joint between the trapezium bone in the wrist and the first metacarpal bone of the thumb. This joint allows for the thumb's opposable movement, which is essential for grasping and manipulating objects, contributing to the dexterity of the human hand.