What is the primary motion of the OA joint?

• A. Rotation
• B. Lateral Flexion
• C. Flexion/Extension
• D. Translation

Answer: (C)

Nodding the head relies mainly on the occipito-atlantal joint, which allows flexion and extension. This joint acts like a hinge in the sagittal plane, letting the skull tilt forward and back relative to the first cervical vertebra. That’s why flexion/extension is the primary motion. There can be a little sideways bending, but it’s limited, and most rotation of the head comes from the nearby atlantoaxial joint rather than the OA joint. Translation is not the dominant movement at this joint.