TMJ and Its Role In Balance

The Temporomandibular Joint

TMJ is the abbreviation for temporomandibular joint. Anatomically, it refers to an area of the cranium where the jaw, or the mandible, contacts and articulates with the temporal bone. The temporal bone is the area of the skull where the ear resides. The TMJ of a horse is more complex than than that of a person. Horses have moveable ears and teeth that erupt throughout their lifetime.

The TMJ consists of bone, cartilage and very sensitive nerves in the condyles of the skull and when damaged causes very severe pain while chewing or with jaw movement. When these bones are misaligned and not articulating properly and the surrounding tissue of the TMJ is stressed, the TMJ Mechanism is out of balance and cannot function optimally.

TMJ issues occur in all types of horses regardless of discipline. Horses exhibit signs of TMJ discomfort in several different ways. Discomfort in the TMJ goes hand in hand with misalignment of incisors and imbalances that may occur in wear of the teeth such as hooks, waves etc.

TMJ Function Effects the Whole Horse

Horses rely on proper function of the TMJ joint in many ways. The ability to move the jaw properly, side to side, forward and back, up and down-not only affects chewing and digestion but also movement and balance. Muscle balance throughout the body is modified and controlled through the TMJ and the function of its suspending muscles. All postural and positional changes of the jaw have multiple effects on structure and function. The horse needs his head to act as a gyroscope, facilitating the fight or flight responses. The TMJ position tells the rest of the body where the head is positioned acting as central routing center.

Dysfunction of the cranial, TMJ, upper cervical or sacral system will profoundly affect the balance of the whole animal, mechanically, physiologically, and emotionally. Unfortunately, pathology in the horse’s mouth can impact the TMJ and create cascading changes down the line. Conversely, problems elsewhere in the body stress the TMJ, and cause unwanted tooth pathology.

The proper function of the TMJ Mechanism therefore plays an important role in the whole function of the horse, including leads, gaits, balance and equilibrium.

Preventive Practices

Grazing is one of the most important ways to prevent TMJ issues. The horse is a grazing animal and depends on the healthy function of his jaw to survive. Grazing allows: the mandible to come down and forward in the joint capsule, the atlantoaxial joint to open, and the mandible to move up and down, side to side forward and back with out any inhibition. It also allows the teeth of the maxilla and mandible to occlude properly. Normally, a horse grazes about sixteen hours a day. For horses who do not get turned out to graze on pasture, such as many performance horses who are kept in stalls, it’s best to have hay available throughout the day - on the ground, not in a rack. It is important that, when a horse eats, his head is down and extended, just like that of a horse grazing.