Synovial joints are the most common type of joint in the human body, allowing for a wide range of motion. They are characterized by a fluid-filled space called the synovial cavity, which is surrounded by a capsule made of connective tissue. This capsule helps to stabilize the joint while allowing for flexibility. The fluid within the synovial cavity, known as synovial fluid, lubricates the joint, reducing friction during movement. Synovial joints include various types, such as hinge joints (like the elbow), ball-and-socket joints (like the hip), and pivot joints (like the neck), each enabling different movements.