Elementary Physiology of the Joints

The shape of the articulating surfaces between the occiput, atlas and axis, define the direction of movements occurring within these joints and concurrently "decide" the muscles stretched from origin to insertion upon subluxation and therefore which muscles will be stimulated (by the nervous system) to work for correction of that subluxation.

Because of the eliptical shapes and complimentary convex-concave surfaces between the occiput and atlas, the lateral movement of atlas’ articular facets on the occipital condyles of the skull necessitates the transverse processes of atlas to rock or slide upwards on the side of laterality accompanying the movement of the articulation.

This would explain the action of the first branch levator working on the side of laterality (ipsilaterally) for the atlas subluxation; pulling the transverse process inferior and thus in the plane of correction laterally (accompanied by the obliquus capitis superior working synergistically on the opposite transverse process).

Whereas the convexity and orientation of the axis superior articular processes in conjunction with its inferior articular processes allows the axis to slide in a rotational plane, perhaps slightly dipping inferior on the side of body laterality.

Similarly, this explains the action of the second branch levator working on the side of ‘spinous laterality’ of the segment, working to correct the anterior and medial movement of the transverse process, upon axis rotation.

Furthermore, the slightly acute angle formed by the first branch levator in relation to the horizontal plane of the atlas, adds to its ipsilateral action.  Whereas the second branch levator is more vertical in comparison, aiding its contralateral action.  This difference in muscle angulation is caused by the extended transverse process of atlas compared relatively short transverse of axis.