How many times have you been to a horse show where you saw a horse owner or handler jerking on the horse’s reins from the ground as punishment for poor behavior? I would expect that most of you have seen this occur at least once if not many times. The following is a list of things to consider when you see someone jerking on their horse’s bit/reins from the ground.
The horse’s skull consists of many bones with most of the joints classified as relatively immobile. These are called fibrous joints or “sutures.” However, there is one major moveable joint associated with the skull. This is the temporomandibular joint or TMJ. There are actually two temporomandibular joints; i.e., there is one on each side of the skull. A simplified description of this joint is that it is formed by the mandible articulating with the temporal bone. Also included in this articulation is the joint capsule, articular disc and ligaments, and all can be subjected to damage.
Because the mandible is a lengthy bone, it can create what we call a long lever arm. According to the mechanics of levers, the longer the lever arm, in this case the mandible (jaw bone), the greater the torque force. Thus, an ounce of pressure, placed on mandible at the bars where the bit lies in the mouth, can translate to pounds of pressure at the TMJ.
Obviously, when we see a handler jerking on the horse’s reins from the ground, there is much more than an ounce of pressure being used. In fact, it’s much more likely that the handler is using a pound or more of pressure on the reins. Consider the repercussions of this.
First, the horse will experience pain on the bars of the mouth, followed by pain at the joints (TMJ) and quite possibly damage to the joint itself. The result may include chronic pain and inflammation surrounding the TMJ as well as tension in the muscles around the joint. Those muscles can eventually become hypertonic and may even become ‘locked’ in spasm. Thus, the pain-spasm-pain cycle well-known to massage therapists is now set up to begin.
The muscles involved might include the masseter, temporalis, occipitomandibularis, obliquus capitis cranialis & caudalis, longissimus capitis, etc., as well as restrictions in the surrounding fascia. Note that all muscles involved have not been listed, so have fun investigating and learning if you choose to pursue this type of study.
In cases where TMJ Syndrome/Disease is suspected, I always recommend veterinary intervention as there can be other causes for this problem. Among these causes are poor dentition, blunt trauma, or a trauma such as getting the face caught in a feeder, fence, etc. Veterinary care is paramount since proper care must include a correct diagnosis of the problem, assessment of the joint itself, dental assessment, and treatment to help decrease pain and inflammation at the very least.
Once the vet clears the horse for massage, the massage therapist should pay special attention to the muscles surrounding the TMJ and the muscles around the lower jaw. Areas of ‘referred pain’ should also be considered. Thus, you should investigate other facial muscles as well as the muscles around the ears and poll.
To find information about these muscles, their attachments, actions, etc., we recommend the study of a good equine anatomy book such as: Textbook of Veterinary Anatomy – Dyce, Sack, Wensing, or Anatomy of the Horse – Klaus-Dieter Budras. Visit the EquiTouch website and use the Book List button to find a more complete listing of anatomy texts.
Future blogs will continue this discussion to include other areas of the body affected and the muscles involved. We’ll also discuss the horse’s automatic response to the handler jerking on the bit as well as behavioral issues the horse may develop as a result.
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