Hinged joints are a type of synovial joint that allow movement primarily in one plane, similar to the way a door swings open and closed. They are characterized by a convex surface fitting into a concave surface, enabling flexion and extension. Common examples of hinged joints include the elbow and knee. These joints are supported by ligaments and surrounded by a synovial membrane, which produces fluid to reduce friction during movement. The structure of hinged joints provides stability while allowing for a range of motion, making them essential for various physical activities and daily tasks.