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 and movement. The synovial fluid within these joints lubricates the surfaces, reducing friction during movement. Common examples of synovial joints include the knee, elbow, and shoulder. These joints are essential for activities such as walking, bending, and lifting, contributing to overall mobility and function.