A horse that tosses his head, worries his bit, acts oddly under-saddle or has issues with specific gaits or leads should have a veterinarian out to rule out lameness or other painful issues. If a definitive lameness can't be determined, the horse may have an issue with his temporomandibular joints (TMJ), which are small bones located just below and in front of each ear.
Other indicators that the horse may be having issues with these joints are uneven wear on his teeth, cribbing, head shyness, ear sensitivity or sensitivity around the jaw. Often riders are the first to notice something is amiss when the horse works under saddle. The horse may play with his tongue or have explosive reactions to being asked to work.
The TMJs can be blocked like any other joint in a horse to determine if they are the source of pain; if the offensive behavior is alleviated or if the horse moves soundly, it's appropriate to believe that the TMJ(s) is the source of pain. TMJ issues, called TMD (temporomandibular joint disease) is difficult to diagnose as it presents similarly to many other issues. It is not known how common TMD is.
Dr. James Carmalt of Western College of Veterinary Medicine (WCVM), University of Saskatchewan recently received a $50,000 grant from the Mark and Pat DuMont Equine Orthopedics Research Fund to further the study of TMJ joints; additional stipends will support the research into TMJ inflammation and equine performance.
Carmalt notes that the causes of TMJ can be varied, but could include the use of hay racks, tight nosebands, uneducated rider hands, improperly fitted saddles, lack of natural grazing posture or poor hoof care (which causes stilted gaits). Additionally, a horse that has his head caught and reacts in a panic may also cause injury to his TMJs. Infection is occasionally associated with TMJ pain, caused by an injection into the joint.
Carmalt says that the disease has been found in all breeds of horses, but not in foals. The research grant will help Carmalt work toward two goals: one is to see if there are differences in joints with and without a meniscus and to see if there are differences between cartilage types.
Four types of cartilage will be harvested from horses that have been euthanized for reasons other than arthritis: these include cartilage from the fetlock, stifle, TMJ and navicular bursa. The cartilage is then grown and treated with lipo-polysaccharide (LPS); the researchers then measure the inflammatory and anti-inflammatory proteins the cells produce. Common treatments will then be tested to determine what works best.
The second goal with the research funds will be to assess the movement of horses on a treadmill, then inject the horse's TMJs with an inflammatory agent. They will then assess the horse again. The researchers hope to prove that inflammation in the TMJ joint can cause poor performance and behavior, and that the joint deserves more attention that it typically receives.
Read more at Horse Community Journals.
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