As a small child begins to run away, the child's parent grabs her arm and pulls her back. The child then complains that her arms hurts. What structure has been injured:
1. biceps tendon
2. radial artery
3. annular ligament
4. olecranon process
5. ulnar artery

Answer: #3, annular ligament, why? The abrupt jerk on the child's arm displaced the annular ligament from the radial head to produce the classic 'nursemaid's elbow'. The cure is multiple pronation and supination movements at the forearm with the arm bent at the elbow.