Osteoarthritis of the Equine TMJ

horse cannot naturally lower its head and eat off the ground. And horses can injure themselves with panic reactions.
In a panicpull attempt to escape a head caught between gate and post situation my Thoroughbredcross youngster sprained his TMJ says Judy Todd a physiotherapist in Abbotsford BC. He had difficulty opening his mouth wide enough for an apple and there were some impressive clunking sounds coming from one TMJ. As a physiotherapist regularly treating human TMJ dysfunction I elected to apply some adapted treatment techniques including heatice liniments trigger point release and joint glides which I approached from the outside of his TMJ. There was no way I was going to lay my thumb down on his back molars as I would for a human! Within a couple of weeks he was functioning normally accepting the bit and expressing no concern with his annual teeth floating.
Carmalt says that when addressing TMD in horses they focus on the intraarticular group of diseases which include sepsis infection or degenerative joint disease such as arthritis. 
This is different to that of humans where intraarticular TMJ disease is only one subclassification of myofascial pain pain caused by muscle tension fatigue or spasm. The reason for this is that we simply do not know if horses get headaches etc. from tight muscles in their heads or other problems. 
The temporomandibular joint in humans connects the lower jaw or mandible to the temporal bone at the side of the head. You can feel the joint by placing your fingers just in front of your ears and opening and closing your mouth. You feel the joint move smoothly up and down and that allows us to talk chew and yawn. Muscles control the joints position and movement.
Carmalt says that infection of the TMJ in horses is sometimes associated with an injection of steroids or some other medication into the joint or it may be related to trauma to the joint. Such conditions are managed by flushing or by careful use of antibiotics. But diseases like arthritis can be more difficult to diagnose. He points out that horses as prey animals do not always exhibit pain to avoid signaling to predators that they are an easy target. If they have some discomfort they will continue to eat normally by compensating and chewing on the other side of the mouth thus reducing pressure on a painful joint.
The challenge is that
there is no one clinical sign specific to TMD. Many of the discomfort signs horses display can often be attributed to other diseases which need to be ruled out before focusing on the TMJ.