The 411 on the TMJ
Dr. Mike Sheets discusses disorders and diseases of one of your horse’s hardest working joints—the temporomandibular joint.
It was the typical one-horse-after-another busy day for Oklahoma veterinarian Mike Sheets, DVM. A longtime client had brought a horse in for an examination. Lately, the seasoned gelding had been breaking in two if his rider pulled on the reins to slow him at the lope.
“He thought it was a dental issue, but I never found anything unusual—mouth or otherwise,” remembers Sheets. “I floated the horse’s teeth and sent him back home.”
When the pair returned a few weeks later with the same problem, Dr. Sheets took a different approach in his examination. He focused not on the horse’s mouth, but his head.
“The horse about banged his head on the stocks when I palpated the TMJ,” shares Dr. Sheets. “It was pretty obvious to me that I had found my culprit.”
An abbreviation for temporomandibular joint, the TMJ is located on either side of a horse’s head just behind the eye. Here, the mandible meets and articulates with the cranium in a hollow area below the temporal bone.
“Most people think of it as the hinge for the jaw,” notes Sheets. “In the horse, the TMJ and its associated muscles, tendons, ligaments, cartilage, and synovial joints work together for balance and to allow the jaw its wide range of movement—side to side, forward and back, and up and down. Because a horse is primarily a grazer, the TMJ is considered the mechanism for mastication [chewing].”
Despite its superstar status, the TMJ is not something you can find a lot of literature on—especially when trying to diagnose an issue, Dr. Sheets shares. In addition to TMJ’s less-than-common denominator for soundness and behavioral issues, symptoms of its dysfunction can range from very specific to not so specific, which often leads veterinarians and owners to target other offenders before eventually considering the TMJ.
Cause for Concern
A horse’s TMJ is affected by many of the same conditions as other joints, explains Sheets. Wear-and-tear (osteoarthritis), bacterial infection (septic arthritis), trauma or misalignment (subluxation), and chronic irritation caused by a litany of known and unknown factors (synovitis), can all prey upon this high-traffic area.
“When a horse with TMJ issues comes in, he might have swelling in that area. He might not. e might noHe might have trauma to and drainage from the TMJ. Or, he might not. His owners might cite his issues as a biting or dental problem—and it might just be a simple need for dental work to repair malocclusions [misalignment of teeth].
“They might share stories about abnormal behavior like head tossing, shaking and shying, bucking when pressure is applied to the bit, resistance to turn on one side, spilling feed, weight loss—the list is as broad as it is long,” confides Dr. Sheets.
“The most frustrating part of working with TMJ issues is in understanding their symptoms and underlying causes. It’s generally not the first thing you look for.”
Palpation of the TMJ area is a good place to begin when trying to diagnose or eliminate TMJ-related problems. However, it is often the last place your veterinarian will start, says Sheets. The palpation of the TMJ in a horse that has issues—with the obvious exception of a visible subluxation or fracture—will generally show tenderness or pain on one side or the other with light pressure. If you have to exert significant pressure to get a reaction, the odds are the horse does not have a TMJ problem.
And while x-rays might be helpful to confirm the extent of a fracture in the joint, as a stand-alone TMJ diagnostic tool, they are generally inefficient as horses with severe arthritis can make pretty pictures, according to Dr. Sheets. Their use might be better suited for future prognosis.
A full dental exam, working from the outside along the cheeks and moving inside to feel and look for sharp edges, abscesses, misalignment, and other potential maladies is where most veterinarians initially start. Any tenderness or stiffness while moving the horse’s jaw from side to side should be noted.
For a more thorough examination, a veterinarian will sedate the horse and fit him with an oral speculum. Sedation is mandatory to avoid resistance and potential harm or instability to the TMJ. Studies have shown an oral speculum can cause TMJ discomfort, but Sheets argues that extended periods of time—more than 15-minute intervals—in a speculum, not the tool itself, are to blame. The instrument is a must-have to safely examine and work on the horse’s back molars.
It is not the time to palpate the TMJ once a horse is sedated, shares Dr. Sheets. Sedatives will often mask any tenderness giving a false impression of soundness.
Dental issues can quickly evolve into TMJ concerns if not confronted and corrected. Teeth continue to grow, erupt and wear down over the course of a horse’s life, which makes dental exams an important part of routine veterinary care. Yearly floating and necessary corrective work helps prevent unevenness.
“Routine dental care can help prevent a lot of future TMJ issues just because a horse is less likely to develop a severe malocclusion over time because it will be addressed at least once a year,” he notes.
According to Dr. Sheets, the most common and conservative treatment for non-septic arthritis and synovial TMJ issues is an injection of a corticosteroid into the joint. His drug of choice has been methylprednisolone acetate, although common joint injections that feature hyaluronate acid are also popular options.
A couple shots were all it took to resolve the TMJ issue permanently in the horse mentioned at the beginning of the article.
“Of the cases I’ve seen, most respond well with this treatment,” says Sheets. “And of those that did not—it provided some measure of relief for what had become chronic arthritis in the joint.”
Dr. Sheets notes he has seen a little over half a dozen TMJ cases in his more than 22 years of practice. However, it does not keep him from considering the problems in this area as a potential cause in hard-to-peg situations involving changes in eating habits, weight loss, behavior, or performance. He hopes that as more information comes out on the subject, instead of being the last thing he and other veterinarians look for, temporomandibular issues can be the first thing they can eliminate in their search.
Dr. Mike Sheets has more than 22 years experience in general veterinary practice with a special interest in equine dentistry. He and his colleagues operate Northside Animal Clinic in Stilwell, Okla., and Vinewood Animal Hospital in Prairie Grove, Ark. He is a member of the Oklahoma Veterinary Medical Association, American Veterinary Dental Society and Association of Equine Practitioners.
The Tense TMJ
Unlocking TMJ tension with equine bodywork therapist Jim Masterson.
Temporal mandibular joint issues will cause tension in the poll, and vice-versa says, equine bodywork therapist Jim Masterson. And conversely, pain or restriction in the poll will affect other parts of the body.
“Issues in your horse’s body have a way of reflecting in his poll and atlas,” explains Masterson. Therefore, tension and pain he might have from a sore back or compensation for pain in other areas—is generally going to collect in these two hot spots.”
And when the poll tightens up, pain radiates into the TMJ and jaw, he notes.
“It's very common for me to find horses with excessive pain and tension in the poll due to sore front feet, who have corresponding pain and restriction in the TMJ, but who have regular dental work done with no serious dental issues.”
Dental issues should be ruled out as the teeth themselves can be directly responsible for TMJ pain or restriction, suggests Masterson. Any horse, especially one that competes or performs for a living should be checked annually by a veterinarian or a trained equine dental technician. Even after a dental problem is corrected, he says, it is a good idea to release the TMJ of any residual restriction.
Other causes of poll pain that can radiate to the TMJ are rider-related, contends Masterson.
“Over-collection directly affects the poll and the TMJ through the use of the bit. Problems can also develop from using or overusing a bit that isn't suited to a particular horse's mouth, especially if dental issues already exist,” he notes.
According to Masterson, by releasing tension in the poll and atlas, you will relieve tension in the TMJ. (see also Bodywork Basics, for poll release and lateral bending exercise, BHN, Sept. 2009.) However, he also suggests the following methods to effectively and safely loosen the TMJ, as well as keep healthy movement in the jaw. These exercises are designed to help release some of the pain and tension, but are by no means a substitute for finding and eliminating the cause of your horse’s TMJ discomfort, he stresses.
Masterson Method for TMJ #1
Place a thumb or fingers inside and on the roof—or palate—of your horse's mouth, and hold it (them) gently there. This will cause your horse to lick, extend his tongue, and move his jaw from side to side, explains Masterson. Your horse will probably try to move his head around and get away at first, so keep one hand on his halter. This is not to keep your horse from pulling away, but to enable you to go with him as he moves his head around.
“As your horse gets used to it, he will even start to enjoy it—especially as he begins to release tension in the TMJ from the movement.”
Masterson Method for TMJ #2
Place one or two fingertips very lightly right on the joint of the TMJ.
“This is using what I call air gap pressure, not to massage the area,” Masterson clarifies, “but to bring your horse's attention to it.”
Keep your fingers very lightly there, barely touching the hair. Once your horse has relaxed watch his eyes as you slowly move your fingers around an area about the size of a nickel. Look for a blink in your horse's eye.
“When you get a blink, stay on that spot—still barely touching the hair—and wait,” he says. “You may have to wait only five seconds, or you may have to wait 30 seconds, before your horse gives you another sign that he is releasing tension. This sign will most often be licking and chewing, or sometimes repeated yawning and shaking of the head.”
If your horse has pain in this area, cautions Masterson, he might not want you to do this. This can be a sign that he needs to release tension there, so stick with it. This above TMJ release techniques also serve as a good way to check for pain or restriction.
“If your horse responds with visual release responses, such as yawning and shaking the head, then he probably had some pain or restriction there,” says Masterson. “The good part about this is that you're already helping him to release it.”
The Man Behind the Method
An internationally recognized equine bodywork therapist for the United States Equestrian Federation Endurance Team and for equine clientele competing in FEI World Cup, Pan American and World Games Show Jumping competitions, Jim Masterson takes a hands-on, integrated approach to equine wellness. Masterson’s self-taught method relies upon the horse’s visual responses to touch in key junctions (poll; neck, shoulders and withers; lower back) to pinpoint and release accumulated tensions that affect performance. The Fairfield, Iowa, professional continues to practice his craft across the U.S. and abroad. For more information on the Masterson Method, available books, DVDs, or to sign up for bodywork courses, visit mastersonmethod.com.