Hinge joints connect two human bones. They're found at the end of these bones and allow for back-and-forth movement. Hinge joints are the most intricate of all human joints, and are grouped under synovial joints.
A hinge joint is a joint that moves uniaxially. Elbows, knuckles and knees are hinge joints. They are designed to allow side-to-side motion along with back-and-forth movement.
The hinge joint is made of strong ligaments, which are covered with cartilage. A small amount of synovial fluid surrounds the joint, lubricating and allowing for pain-free movement. Synovial fluid is a thick, egg-like fluid found throughout the body, particularly around hinge joints.
The ligaments that make up a hinge joint both allow movement and limit motion at the same time. This directs the movement of the hinge joint and allows for greater back-and-forth movement with a limited side-to-side range. For example, the knee joint can move back and forth easily, but has limited motion side to side.