When do bones allow movement to occur?

Bones allow movement to occur when they are joined together at joints. Joints are points of contact between two or more bones, and they are the structures that provide support and facilitate movement. There are three main types of joints:

- Immovable joints: These joints do not allow any movement between the bones that they connect. Examples include the joints between the bones of the skull.

- Slightly movable joints: These joints allow a limited amount of movement between the bones that they connect. Examples include the joints between the vertebrae of the spine.

- Freely movable joints: These joints allow the greatest amount of movement between the bones that they connect. Examples include the ball-and-socket joints of the hip and shoulder, and the hinge joints of the knee and elbow.

The nature of the movement that is possible at a joint depends on the type of joint and the structure of the bones that form it. For example, ball-and-socket joints allow for a wide range of movement, including rotation, flexion, extension, and abduction, while hinge joints only allow for flexion and extension.