This bone’s name comes from the meaning, “shaped like the letter upsilon (Y)”. I like this kind of trivia.
It is the only bone in the skeleton not articulated to any other bone and held in place by ligaments. Although present in many mammals, the Hyoid bone is uniquely located lower in Homo Sapiens allowing the production of sounds which give us the capability of speech. It is also called the Lingual bone, in reference to the ability of human speech.
Horses can show signs of discomfort with their tongue taking form in sensitivity when touching their jaw or being head shy, or resentment of the bit and/or difficulty to flex at the poll. Chewing more on one side and/or dropping food, along with misalignment of the upper and lower incisors are also signs of distress and discomfort in the tongue.
These and other signs can indicate or could be a possible cause of TMJ or temporo mandibular joints dysfunction.
However another joint which is connected and affected by the condition of TMJ dysfunction is that of atlanto axial joint. It is the area where the first cervical vertebra (atlas) articulates with the second cervical (axis).
Proper training techniques are a very important when considering all these possible issues. A tight or incorrectly adjusted noseband, wrong choice of bit and/or pulling the horse´s nose to his chest (RollKur or hyperflexion or behind the vertical) are all to be avoided.
Practicing flexion of the jaw, originating from the base of the neck - this is not a ´neck in´, but a rounding or curving of the neck from its base to the poll - helps with self-carriage which in turn helps avoid distress to the tongue and thus the TMJ.
And this is when a horse may suffer ´bridle lameness´.
If a horse sticks his tongue out, or appears to flick his tongue, it is a sign of pulling hands. The tongue and larynx both being attached to the Hyoid apparatus this tells us his breathing is being interfered with. Being such a crucial part of the anatomy involved in the effect of aids from the hands, legs or seat, the Thyrohyoid bone is not to be ignored. Riding bitless avoids many of these issues from the start.
Unable to swallow as body function dictates or suffering the tongue discomfort that may lead on to uneven tooth wear etc goes on to present itself in a short, choppy movement in the fores, or maybe hitching up one hind. With no apparent heat swelling or pain in the limbs it is not noted as an otherwise ´regular´ lameness. Some horses may stumble on the fores or have a hind buckle under them. Uneven striding is another sign of this bridle lameness, along with a change in attitude of the horse. As individuals there is no order in which these problems express themselves.
In the longer term there are visual changes in the body. Tightness at the poll is common, to diminishing top-line and even ewe neck. The list goes on.