TMJ tenderness can produce rein lameness

I just read an article on ‘The Horse’ about the TMJ causing rein lameness. Essentially what the said is if there is inflammation in the TMJ then the horse is more likely to respond poorly in some way to rein contact.
Ok, one more thing to check out when a problem arises. But, the article did not mention causes or solutions.
I feel like I’m hanging a bit…


Rein lame is one of those rather diffuse concepts. I’ve always heard it used to describe situations where bad riding is causing a detrimental effect in how the horse moves. For instance riding curled under on the forehand so not tracking up behind. Or riding inverted so not tracking up. Etc. Of course when you are just watching a crap lesson program or crap fake dressage from the bleachers you don’t always know if any given horse also has a physical reason for looking lame.

So unless this author defines how they understand rein lame, it’s hard to evaluate what they are saying.

It could absolutely be true that a sore jaw impacts correct bit contact.

But TMJ is a currently popular and rather mystified body part for both horses and humans. It gets asked to explain a lot.

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There are many potential caused of TMJ issues, from poor dental work, to poor management of the head/neck during dental work, to inappropriate use of German Martingales and draw reins and “head set” devices, to horses being stupid, to bad chiropractic work, to (oddly enough) hind end issues, and who knows what else.

So the solutions depend on the cause.

Expert: Equine TMJ Changes Common, but Clinical Signs Rare – The Horse
TMJ Problems in Horses - Kentucky Equine Research (

and I assume this is the article you read
Rein-Lameness Associated With TMJ Pain in Horses – The Horse

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JB yes, it is, I should have included the link.

thank you.

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I’ve been experiencing something related with my horse, he shows clear discomfort trotting with his bit (even with no contact on the reins), but doesn’t show signs in a bitless.

Well hopefully one of these articles will help you.

Wondering, how long has he been under saddle? It took one of mares a couple of years, no really, before she really accepted having a bit in her mouth. I tried many bits, much $$ then went to a rubber Happy mouth again, she accepted that, but still had a busy mouth, went through 2 HM bits, then I went back to a french link and she accepted it,
She always had a busy mouth, sometimes when really in the zone in a lesson she would get quieter but every halt her mouth got busy…maybe this is your guy?

As someone with awful TMJ pain, I worry about this in my horse a lot. The diagnosis and treatment in humans is terrible, so I can’t imagine how bad we are at recognizing and treating anything beyond a simple case in horses.

Thanks for sharing the links.


that makes sense, as most horses with a bit in will do something with their jaw, whether to “hold” the bit or move it around or something. Poor guy.

Sure can cause issues. If you want some good reading, read about the stomatognathic system. It can be a little “what came first- the chicken or the egg” , so you have to treat the whole system.

A good veterinary chiropractor is beneficial as they may be like, we can adjust- but we need farrier radiographs to ensure the front end is still balanced. Definitely appropriate dental. Equipment check- a lot of bits - even the most simple of simple- cause issues because the horse simply cannot close their mouth completely- aggravating the TMJ under saddle. It’s amazing if you radiograph the bit in the horses mouth just stationary how much it can affect the TMJ positioning.

Though farrier based- look up the Equine Documentalist - he talks a lot on the myofascial connections as well.

Enjoy the rabbit hole!!

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I’ve had him 8 years - got him off the track as a 3 year old. I’m not even talking fussy in the mouth (though he can be), but trotting with bit he is slightly head bobbing lame. Seems ok at walk and canter.
I had my vet look at him about a month ago, he watched me ride, did standard flexion and neuro, then watched him free lunge in round pen. Vet (boards at my barn and knows me and hoese very well) looks at me and says asks if I’m comfortable getting on him bareback with the halter, which I do on occasion. So I got on him in the round pen, trotted no head bob. Vet said possible TMJ or maybe even neck, but said horse was also quite stiff in stifles so ride bitless and strengthen that first if horse seems comfortable enough, then see where we’re at. Vet said let him carry his head/neck however he wants just get him forward and pushing. He’s a naturally lazy horse so it’s work, and hard to tell sometimes if he’s hurting or just his usual lazy self.
He got a chiro adjustment, addressed tightness in TMJ and neck (though chiro didn’t see anything radically amiss).
I gave him over a month of light riding/stifle strengthening in a bitless. Then took both bridles to the arena, warmed up bitless then put bit on (Myler comfort snaffle) and still some head bobbing at trot even on a totally long rein, but at this point I don’t know of its psychosomatic or real pain. So now trying a combination with bit in horse’s mouth but reins attached to side pull. He seems to be trying to figure out what’s going on, where he wants to carry his head and has taken a few gimpy steps but not as bad as eith just the bit.

So sorry for the long saga, if anyone’s bothered reading through and has ideas let me know!


I am scheduling a follow-up with the vet, but thought this was pretty interesting: horse continues to feel okay in a side pull and uncomfortable with a bit - but also showed a similar level of discomfort with a bosal. :thinking:

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Good morning,

I am the author of the paper and have just joined this site having read your post. I am happy to answer any questions that you may have.

I also have a Facebook page (equinetmjdisease) for discussion of this problem with like-minded people. It is NOT for promoting products, training methods, or anything else, but please feel free to submit a request to join if you are interested.

Thank you,

James Carmalt
Professor of Equine Surgery, Dentistry, Sports Medicine & Rehabilitation
Western College of Veterinary Medicine,
University of Saskatchewan


Tried to find your FB page with that name and it didn’t pop up. Would you be able to PM me the link, or post?

Ooops - found it!

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There was a recent post regarding bridle fit/how poorly fitted cheek pieces can lead to discomfort.

"…we often seen poorly fitted cheek pieces, they are often too high up digging into the Browband or sit next to or lying on the sensitive TMJ.

The cheek pieces should run parallel with the facial crest and the buckles should be level or slightly below the corner of the eye to ensure that they are fitted correctly. This is to reduce pressure on the sensitive facial nerves.

Pressure on the TMJ can at the least be irritating ( imagine walking with a small some in your shoe but not allowed to take it out ) but can also cause behaviour and performance issues. This is why it is so important to ensure that they cheekpieces are fitted correctly."

I have zero idea how much truth there is to this, but it’s something to think about for sure.

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