Extension is defined as what happens to the angle between the bones at a joint?

• A. Angle increases
• B. Angle decreases
• C. Rotational movement
• D. Lateral flexion

Answer: (A)

Extension is the action that increases the angle between two bones at a joint, effectively straightening the limb toward its neutral position. This is why extension is described as increasing the angle between the bones. For example, straightening the elbow from a bent position or extending the knee increases the angle between the thigh and lower leg. In contrast, flexion decreases that angle by bending the joint; rotation involves turning around a long axis; and lateral flexion is side-bending of the trunk or neck.