What type of joint allows free movement and contains a fluid-filled cavity?

Synovial joints are characterized by a fluid-filled cavity known as the synovial cavity, which allows for a wide range of motion. This fluid serves as a lubricant, reducing friction and facilitating movement between the articulating bones. The structure of synovial joints includes various components such as articular cartilage, synovial fluid, a joint capsule, and ligaments, all contributing to their ability to allow extensive mobility compared to other types of joints.

These joints can take various forms, including hinge joints (like the elbow) and ball-and-socket joints (like the hip), but the defining feature across all synovial joints is the presence of that fluid-filled cavity. This differentiates them significantly from cartilaginous and fibrous joints, which do not feature such cavities and typically allow for limited or no movement.