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The TMJ and the Tail of the horse

Can you relate?

Does your horse hold their tail to one side?

Is your horse inconsistent in the contact?

Is your horse heavy in the contact?

You are not alone.

I hear you and would like to explain the importance of highlighting the TMJ and Tail to your practitioner or veterinarian.

Let's start with the TMJ

The temporomandibular joint (TMJ) is a complex joint which varies from Horse to Horse depending on their conformation. It is a joint made up of fibrocartilage and research has also shown that there is hyaline cartilage.

The TMJ joint itself is known as a condylar joint suggesting that it has a range of movement in a gliding, rotating and lateral direction. It is a joint that if you look from the top of a Horses head downwards is not a straight line joint and almost at a 15° angle.

When assessing and palpating the TMJs it is important to focus on the right to left joint range of movement and not assume that if both joints are limited in range of movement that there is necessarily an issue. Assessing the entire skeleton particularly around jaw alignment, dental work and front limb, thoracic sling alignment is important. This is because of the surrounding structures including the hyoid apparatus, sternum and tongue which have an impact and correlation to mastication.

There are small and big muscles associated with the TMJ and that besides the big muscle of the macerator found on the outside of the mandible, there are smaller muscle groups such as the digastric muscle which is found on the inside of the mandible and are responsible for opening the jaw. A lot of the other muscles are responsible for closing the jaw and the movement of opening the jaw is actually more of a passive movement. Now this makes sense from a gravity perspective and the fact that horses are on four legs with their jaw hanging down

There are small supportive ligaments that are surrounding the TMJ joints and are key in stability and support of this area. They can be many causes of TMJ issues and if incorrect dental care, usage of tack or trauma or conformational defect such as parrot mouth can directly impact TMJ stability and function.

Common diagnosis of TMJ issues can be osteoarthritis with symptoms of TMJ function or dysfunction include head shaking, beating issues, trauma, nerve damage to the cranial portion.

It is also important to remember the surrounding soft tissue structures and connections lower down, for example if a horse is diagnosed with osteoarthritis or dysfunction of the cervicals, then this will have a direct impact on TMJ mobility and range of movement. Similar with issues through the lower or upper cervicals, shoulder, thoracic sling region will also have an effect on TMJ functioning.

The Tail

The tail is commonly misdiagnosed because it is poorly understood. There are very limited anatomical and biomechanical studies out there showing the effect of the tail or what effect trauma to the tail has on the biomechanics of the spine.

The tail has a variation in vertebrae compared to the rest of the spine. The transverse processes of caudal vertebrae Ca1 and Ca2 are different to that of the rest of the caudal vertebrae, which decrease and change shape lower down the tail.

There are 12 muscles which run around the tail and their names are dependent on whether they are dorsal, medial, lateral or ventral. The dorsal tail muscles will be responsible for extension of the tail whereas the ventral muscles of the tail will be responsible for unilateral or ventral flexion of the tail.

When assessing the tail, we must focus on the tail in the stable compared to when there is tack and then compared to when the horse is being ridden. When assessing the tail symmetry it is important to stand the horse up completely square behind on a level surface. There are many ways to assess the tail but fundamentally you are looking for tail set, low or high, symmetry right to left, running a line down the sacrum and tail, you want to see equal sides of the tail down each line.

Look out for obvious signs of trauma such as deviations of the tail, muscle asymmetries of the hind quarters or of the tail muscles themselves and any lumps or bumps that should not be there.

How does this apply from a practical perspective ?

Case Study:


7 year old, gelding, in medium work (ridden 4 days per week).

Having listened to the owner and asking further questions to build a history, below is a summary of the symptoms presented.


  • Tail held left naturally (no rider on board)

  • Tail positioning left increased with the rider and saddle

  • Horse was struggling to canter right - weak unbalanced and the owner felt like she was having to hold the canter together on the right rein.

  • Difficultly bending to the right.

  • Inconsistent in the contact

  • Intermittently the horse was showing signs of discomfort by being reluctant to open he’s mouth for the bit and bridle

Observation 👀

Before I do any form of treatment, I watch the horse in their movements around the stable, their interaction with the owner, how they naturally want to stand, eat and be. I then like to watch them move, preferably in all paces and on both reins. In some cases I will also watch them with the saddle on and then with the rider. It’s almost like a process of elimination with horses and at each stage I am watching their behaviours and movements.

Palpation and Treatment:

When it came to Bruno, I noticed that he was chewing he’s food in a very fixed pattern and was slightly tilting he’s head when eating hay off of the floor. After further assessment, it was clear that Bruno was using the TMJ on the left more than the right and that the signs of discomfort with the bit and bridle were possibly due to an asymmetry through the TMJ on the right and the OA joint right.

This was only part of the picture.

Further palpation confirmed that Bruno was offloading he’s weight onto the left shoulder due to a dysfunction through the shoulder girdle. The sternum and barrel was off set to the left of he’s midline. Again, this is only part of the puzzle piece, but from an anatomy perspective, after I treated the TMJ on the right, the OA joint right, shoulder girdle left and sternum left, Bruno started standing straighter in front and was eating the hay off of the floor with no head or neck tilt.

There was still the issue of the tail and barrel, not surprising as everything is connected!

Before treating the mid region of the body, I moved onto the pelvis and sacrum symmetry. Bruno was showing a body pattern of a pelvic drop through the pelvis to the right with associated muscle hypertonicity to through the extensor chain muscles and tail muscles on the left. The question I was asking myself was whether the pelvis was causing the tail to move left or were there issues with the muscle contractibility of the extensor chain to the left?

There are no right or wrong thoughts here, the most important thing is to ask questions and remain curious. When I reassessed the body, the owner and I started seeing Bruno’s posture changed before our eyes! He was stood more square behind, the tail was straighter and he’s breath slowed down. Treating and guiding the body towards a better alignment also, helped the barrel. Bruno walked out of the stable with he’s tail completely straight, he’s steps were move equal, there was equal and rhythmical swing to the barrel and he looked more comfortable overall.

What happens next?

Each horse is different and there is no recipe for the body. I tailored the aftercare to suit what I treated on Bruno in relation to he’s management.

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