The equine neck consists of seven vertebrae, which articulate in different directions via intercentral joints and articular process or facet joints.
The greatest range of motion — extension and flexion, lateral bending and rotation — occurs between the fifth cervical and the first thoracic vertebrae. Even clinically normal horses will show X-ray abnormalities involving the articular process joints between these vertebrae, reflecting osteoarthritis.
Various muscles and ligaments attach to the neck vertebrae and influence their movement. In most horses, there is left-right symmetry between the vertebrae and the muscular attachments. Some, however, are born with asymmetry of both the bones and the soft tissues. Suffice to say, some world-class horses have had such abnormalities with no associated clinical signs.