What is a characteristic feature of synovial joints?

A fluid-filled joint cavity is a defining characteristic of synovial joints. This cavity, known as the synovial cavity, is filled with synovial fluid, which plays a crucial role in reducing friction between the articulating surfaces of the bones during movement. It also helps to nourish the cartilaginous surfaces of the joints and acts as a shock absorber, making these joints capable of a wide range of motion.

In contrast, synovial joints are not rigid structures; they are specifically designed to allow for movement, which differentiates them from other joint types like fibrous or cartilaginous joints. Additionally, the presence of synovial fluid means that these joints are well-lubricated, facilitating smooth movements rather than bone-to-bone connections without lubrication, as seen in other types of joints. The extensive range of motion permitted by synovial joints is an essential feature that supports various activities and functions in the body.