What does "extension" mean in the context of joint movement?

In the context of joint movement, "extension" refers to the action of straightening or extending a joint angle. This movement increases the angle between two body parts, moving them further apart. For instance, in the case of the elbow, when the arm is straightened from a bent position, this action is considered extension. This term is commonly used in the context of various joints in the body, such as the knees, hips, and fingers. Understanding this concept is crucial for analyzing movements in physical activity and exercise, as it plays a significant role in functional anatomy and the mechanics of human movement.