Which classification of diarthrodial joint allows for side-to-side and up-and-down movement?

The classification of diarthrodial joints that allows for side-to-side and up-and-down movement is the saddle joint. This type of joint is structured to permit movement in multiple directions, typically allowing for a greater range of motion than hinge or pivot joints. In a saddle joint, the opposing surfaces are shaped like two saddles facing each other, which allows for flexion, extension, abduction, adduction, and circumduction.

For instance, the carpometacarpal joint of the thumb is a well-known example of a saddle joint, enabling the thumb to move side-to-side and up-and-down in a way that facilitates its grasping function. This flexibility and combined movement capability differentiates saddle joints from hinge joints, which primarily allow movement in one plane (flexion and extension), and pivot joints, which allow for rotation around a single axis. Condyloid joints also permit movement in two planes but typically do not allow as much freedom for side-to-side motion as saddle joints do. Understanding these distinctions helps clarify the functional capabilities of the different joint classifications.