Joints that give a YES/NO sign in the neck
- Lateral bending (cocking the head)
- There is no movement at the median atlanto-axial joint. There is a total of 8 degrees of motion: 3 degrees at the atlanto-occipital joint, and 5 degrees at the zygapophysial joints of the axis and the third cervical vertebra. The motion at the zygapophysial joints of the lower cervical vertebrae combined with the motion at the zygapophysial joints of the lower cervical vertebrae results in 45° of lateral bending motion.
- Flexion and extension (nod: YES sign)
- The atlanto-occipital joints are capable of flexion and extension of 15 degrees each. In addition to this, motion at the atlanto-axial joints (lateral and median atlanto-axial joints) is added, allowing 20 to 30 degrees of flexion and extension at the upper cervical vertebrae. In addition, the motion of the lower cervical vertebrae is added, and the total flexion and extension motion is 130° (based on the occlusal plane of the dentition).
- Rotation (NO sign)
- A total of 80 to 90 degrees of unilateral rotation is possible, including 12 degrees at the atlanto-occipital joint, 12 degrees at the atlanto-axial joints (lateral and median atlanto-axial joints), as well as at the zygapophysial joints of the lower cervical vertebrae.