Synovial joints are the most common type of joint in the human body, allowing for a wide range of movement. They are characterized by a fluid-filled space called the synovial cavity, which helps reduce friction between the bones. This type of joint includes familiar examples like the knee, elbow, and shoulder, enabling actions such as bending, twisting, and lifting. These joints are surrounded by a tough capsule made of ligaments that provide stability. Inside the capsule, synovial fluid lubricates the joint, nourishing the cartilage that covers the ends of the bones. This unique structure allows for smooth and efficient movement, essential for daily activities.