Neck pain and stiffness are common problems veterinarians treat in performance horses. And it’s no wonder, considering the length of the equine neck and its necessary function in turning, balancing, collecting, and—unrelated to performance—grazing. Scientists recently showed that even horses without obvious signs of neck pain or stiffness might have abnormal bony changes there.

While veterinarians commonly image the neck and inject the cervical vertebrae for pain management, there’s little research describing bone pathologies in the equine neck, said Kevin Haussler, DVM, DC, PhD, Dipl. ACVSMR, of Colorado State University, at the 2017 American Association of Equine Practitioners’ Convention, held Nov. 17-21 in San Antonio, Texas.

To better understand equine neck issues, Haussler and fellow researchers investigated the cervical spines of euthanized horses, resulting in their study, “Characterization of Bony Changes Localized to the Cervical Articular Processes in Horses.” The team included Hilary Clayton, BVMS, PhD, MRCVS, Dipl. ACVSMR, and Roy Pool, DVM, PhD.

The horse’s neck includes seven cervical vertebrae (C1 through C7, basically the poll to base of the neck), each of which has bony protrusions called articular processes that interlock with the adjacent vertebrae.

Where the articular process meets the next vertebrae is called the “articular facet.” Like links in a chain, the articular processes allow the horse’s spine to move. When bony changes happen along these links, horses can experience significant and even career-ending neck stiffness and pain.

In the study, Haussler and his team looked at C2-T3 (the third thoracic vertebrae) of 56 horses that died for reasons unrelated to neck or wither pain. The horses had participated in various disciplines and were different breeds, ages, heights, and weights.

Of these horses, most (72%) had abnormal bony changes in the neck. These abnormalities affected all vertebral levels from the head to the lower neck, and grades of severity ranged from mild (28%) to moderate (22%) to severe (5%).

The researchers found that many bony changes were related to osteoarthritis and muscle and joint capsule entheses (connective tissues), said Haussler, and many horses exhibited more than one issue.

“Older and taller horses had an increased prevalence and severity of disease,” Haussler said.

The researchers concluded that even though veterinarians image necks frequently, many pathological changes aren’t likely visible via routine radiographic imaging, and horses might have changes without showing obvious signs of discomfort. At this time, it is unclear which specific bony changes contribute to neck pain and stiffness, Haussler said.