Willoughby said that chiropractors deal almost exclusively with the pathologies and dysfunction created by vertebral subluxations, but that the traditional veterinary definition of a subluxation as an incomplete or partial dislocation is not an accurate definition of the vertebral subluxation as described in chiropractic. Altered nerve transmission is caused by pressure or traction on a nerve, changes in cerebrospinal fluid flow, vascular flow to neural tissues, or alterations in axoplamic flow. Adjusting skill depends on knowledge of vertebral anatomy, according to Willoughby. She admonished that the practitioner must know vertebral joint relationships, the location and orientation of osseous processes, the relationship of neural components, muscle attachments and nerve supply, vertebral joint anatomy, and normal and abnormal range of motion. The equine vertebral column is a flexible structure that permits the horse to perform in a wide variety of athletic endeavors, such as lowering the head, arching the back, and lateral bending.
Spinal movements consist of flexion-extension, axial rotation, and lateral flexion.
The equine vertebral column has over 170 joints. The vertebral column is also subject to movements and forces from compression, tension, vertical shear, and horizontal shear. Most veterinarians experienced in lameness work are likely to be very astute at these first aspects of chiropractic. The two palpation procedures, however, seem to require special knowledge and experience in light of the complex nature of the equine vertebral column and the heavy muscles which can only make palpation of this structure more difficult. Static palpation allows the practitioner to analyze osseous segments and their processes, according to Willoughby.