Which of the following movements involves extending a joint?

The correct answer is extension, as it specifically refers to the movement that increases the angle between the parts of a joint. When you perform extension, you straighten a flexed joint, which generally moves a limb back toward its anatomical position. For instance, when you straighten your arm from a bent position at the elbow, you are extending the joint.

In contrast, flexion, which is the opposite movement, involves decreasing the angle at a joint, such as bending the elbow or knee. Abduction and adduction refer to movements toward or away from the midline of the body. Abduction moves a limb away from the body, while adduction brings it closer to the midline. These movements do not involve extending a joint. Understanding these definitions helps clarify how joints move in relation to one another, particularly regarding the processes of extension and flexion.