What defines a sliding/plane joint?

A sliding or plane joint is characterized by its ability to facilitate a gliding or sliding movement between two surfaces. This type of joint allows the connected bone surfaces to move past each other in a linear direction without any significant rotational capability. This sliding motion is crucial in various anatomical functions, as it enables movements such as shifting and repositioning without the constraint of rotation around an axis.

The other choices suggest functionalities that do not align with the defining characteristics of a sliding joint. For instance, rotary motion, fixed positioning, and multiple axes of rotation describe other joint types, such as ball-and-socket joints or hinge joints, which are specific to different degrees and types of movement. Thus, the focus on sliding motion aptly highlights the unique function of a sliding or plane joint.