Which term refers to the action of increasing the angle of a joint?

The action of increasing the angle of a joint is referred to as extension. This movement occurs in various joints throughout the body, such as the elbow, knee, and spine. When a joint extends, the two bones forming the joint move further apart, resulting in a larger angle between them. For example, straightening the arm after a bicep curl or straightening the leg while walking demonstrates extension in action.

Flexion, in contrast, is the action of decreasing the angle between the bones of a joint, such as bending the elbow or knee. Dorsiflexion specifically refers to the movement of the foot which involves raising the toes and foot upward toward the shin, and lateral flexion pertains to bending the spine to the side. These terms describe different movements and angles, further clarifying why extension is the correct term for increasing the angle of a joint.