The frontal plane spinal action of the psoas major is fairly clear; it crosses the spinal joints laterally, so it lateral flexes the spine to that side.
Motions of the Cervical Spine
Table 1 shows average healthy ranges of axial motion of the cervical spine (head and neck), from the atlanto-occipital joint through the C7-T1 joint.
Cervical Spinal Joints
The disc joint is a cartilaginous joint that is composed of outer fibers called the annulus fibrosus that encircle the inner nucleus pulposus.
