Which movement increases the angle of a joint?

• A. Flexion
• B. Extension
• C. Abduction
• D. Circumduction

Answer: (B)

Extension increases the angle between bones at a joint, effectively straightening the limb. For example, when you straighten a bent elbow, the angle between the upper arm and forearm grows toward a straight line. Flexion does the opposite by decreasing that angle. Abduction is movement away from the body's midline, and circumduction is a circular motion that combines several movements; neither is defined primarily by increasing the joint angle in one plane. Therefore, extension is the action that increases the angle.