Final answer:
Synovial joints have a joint cavity that contains synovial fluid, allowing for high mobility and less friction, unlike fibrous and cartilaginous joints which are directly connected by connective tissue or cartilage.
Step-by-step explanation:
Synovial joints are different from both fibrous and cartilaginous joints because synovial joints have a joint cavity filled with synovial fluid. This unique structure provides lubrication that reduces friction and allows the bones to move freely against each other, resulting in greater joint movement and mobility. In contrast, fibrous and cartilaginous joints do not have this space; their articulating bone surfaces are directly connected to each other with fibrous connective tissue or cartilage, limiting their movement. The ends of the bones in synovial joints are also covered with a smooth articular cartilage, and the joint is surrounded by an articular capsule that supports movement while resisting dislocation.