Ball and Socket Joints

These are found in the shoulder and the hip. They allow a circular movement in these joints. At the shoulder the 'ball' is part of the humerus, the long bone in the top of the arm. The 'socket' is formed by the scapula or the shoulder blade. The muscles joined to these bones allow a circular movement when they contract. In the hip it is the femur which provides the 'ball'. The pelvis, or hip bone, provides the socket.

Hinge Joints

These are found at the elbow and the knee. They allow a movement of 180° in one direction. Try moving your arm at the elbow. It can only move in a half circle (180°) and only up and down. Now move your arm from the shoulder and see the difference.

Semi-movable Joints

These joints only move slightly. They can be found in the backbone. The backbone is made of many small bones called vertebrae. Each one of them is called a vertebra. The semi-movable joints are between the vertebrae. Because there are so many vertebrae there are many semi-movable joints.

Each one moves very slightly but when they move together it make the movement more obvious.

Immovable Joints

These joints do not move at all! You can find them in the skull. they have grown together like a very complicated jig-saw puzzle. When babies are born care is taken not to bump their heads. This is because the bones in the head are still soft and have not yet grown together. Within a few months the bones meet each other as the baby grows. Eventually they are so well held together that they are impossible to separate.

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