TMJ Problems in Horses

The temporomandibular joint (TMJ or jaw), like any other joint in the horse’s body, can be a source of pain. Because horses spend a substantial portion of each day eating and grazing, TMJ dysfunction and pain can negatively affect the horse’s overall health.

“TMJ disorders, such as osteoarthritis, can alter feed intake, interfere with the horse’s ability to masticate their food appropriately, and even result in deformed dentition,” advised Catherine Whitehouse, M.S., a Kentucky Equine Research nutrition advisor.

In humans, approximately 12% of the population suffers TMJ dysfunction, and this is an increasingly recognized problem in other species, such as dogs and cats. Like humans, the TMJ of horses is comprised of the lower jawbone, or mandible, and the upper jawbone, or maxilla, on both sides of the head and a cartilage disc nestled between those two bones within the joint. Other than its basic anatomy and despite the obvious importance of this joint, little information exists regarding the TMJ in horses.

To improve the industry’s knowledge about the TMJ and its associated dysfunction, one veterinary team* examined TMJs from 16 horses. They found that the disc, thought to cushion the joint, varies in stiffness depending on its location within the joint and based on the age of the horse. According to the researchers, “mechanical demands on the TMJ disc differ between horses and other species.”

“Like any joint in the horse’s body, prophylactic administration of joint supplements will help maximize the health of the TMJ joint. Such products include KER-Flex ( look for Glucos-A-Flex in Australia), Synovate HA, as well as EO-3 with anti-inflammatory properties proven to benefit horses with OA,” Whitehouse said.

“This study also shows that not all difficulties associated with food consumption in horses can be blamed on dentition alone,” advised Whitehouse.

*Guerrero Cota, J.M., D.M. Leale, B. Arzi, et al. Regional and disease-related differences in properties of the equine temporomandibular joint disc. Journal of Biomechanics. In press.