The type of joint that is distinguished by having a fluid-filled joint cavity is called a _____________ joint.

A joint characterized by a fluid-filled joint cavity is classified as a synovial joint. Synovial joints are designed for movement and flexibility, containing synovial fluid within this cavity, which acts as a lubricant to reduce friction between the articulating surfaces of the bones. This fluid-filled space also facilitates the nourishment of the cartilage covering the bone surfaces, enhancing joint health and function.

In contrast, fibrous joints do not have a joint cavity and are connected by dense connective tissue, which limits mobility. Cartilaginous joints are also different in that they are joined by cartilage and do not have a fluid-filled cavity, allowing for limited movement. Sutures, a specific type of fibrous joint found in the skull, also lack a joint cavity and are immovable. Thus, the defining feature of a synovial joint is its fluid-filled cavity, which is critical for its functionality and mobility.