An introduction to the equine and canine hyoid apparatus
After I attended CPD training on the holistic assessment and treatment of the equine and canine hyoid, I did a poll on my Instagram stories asking who had heard about the hyoid. Everyone that responded had no idea and wanted to know more. So here is a blog for you...
I'm not going to lie; I went down several rabbit holes researching this little fella. Well, I say little; the hyoid is a key structure that despite being small in size, is MIGHTY in function.
I am going to tell you about the structure in both horses and dogs, but you can easily scroll to the section that you're interested in. You will see that there are some differences between the two. Hopefully this will be useful for both owners and therapists alike. I am going to try to keep it simple, because this can get complicated, but if you're desperate for more let me know!
Anatomy - equine
Stylohyoid - insertion attachment for the occipitohyoid muscle
Epihyoid - these 2 bones connect to the stylohyoid and ceratohyoid
Ceratohyoid - these 2 bones connect to the stylohyoid and basihyoid
Basihyoid - insertion attachment for the sternohyoid and omohyoid muscles
Thyrohyoid - insertion attachment to the thyrohyoid muscle (hyoid to thyroid cartilage)
Lingual process - insertion attachment for the tongue, where the bone is embedded
Muscle Focus - equine
So let's explore the muscular attachments in more depth. You can clearly see from the visuals below that the hyoid has significant connections throughout the whole body via muscular and fascial chains. Can you appreciate how EVERYTHING is connected - it is quite remarkable. To take this message home, quite often I see imbalances in the jaw, sternum, shoulder and pelvis - assessment and release of the hyoid can help target all areas.
Dorsal chain - the muscles making up the top line of the horse, located above the spine and behind the hip. This chain facilitates all forward movement, and is also known as the extensor chain.
Ventral chain - the muscles making up the underside of the horse, located underneath the spine and in front of the hip. This chain facilitates correct posture of the back (through core engagement of the abdominals) and collection, and is also known as the flexor chain.
OCCIPITOHYOID - attaches the hyoid to the occiput (skull)
STERNOHYOID - attaches the hyoid to the sternum (chest)
OMOHYOID - attaches the hyoid to the scapula (shoulder)
Things to consider:
The equine hyoid is sometimes referred to as the 'tongue bone' because of it's primary muscular attachment to the tongue. Any restrictions to the tongue can go on to ignite a muscular chain reaction and have GLOBAL effects on the body and biomechanics, which is why it is arguably one of the most important anatomical structures.
Common factors affecting the hyoid and tongue include:
dental issues
a poorly fitted bit / bridle
windsucking / cribbing
TMJ (temporomandibular joint) / poll / jaw tension and asymmetry
How will this present in the horse?
Shortened forelimb stride
Lacking engagement from the hindlimb
Avoiding contact with the bit / going behind the vertical to relieve tension at the poll
TMJ sensitivity (pain on palpation)
Restriction in lateral bend and flexion of the neck
Lack of swing to the muscles on the underside of the neck (appearing fixed and hypertonic)
Inhibited action of the abdominals to lift and engage the back
Anatomy - canine
Stylohyoid - articulates with the temporal bone of the skull, allowing a pendulum movement between the tongue and larynx
Epihyoid - these 2 bones connect to the stylohyoid and ceratohyoid
Ceratohyoid - these 2 bones connect to the stylohyoid and basihyoid
Basihyoid - insertion attachment for the sternohyoid muscle
Thyrohyoid - insertion attachment to the thyrohyoid muscle (hyoid to thyroid cartilage)
Muscle Focus - canine
GENIOHYOID - attaches the hyoid to the mandible (jaw)
STERNOHYOID - attaches the hyoid to the sternum (chest)
MYLOHYOID - attaches the hyoid to the tongue
NB. unlike horses, the dog's hyoid does not have a direct muscular attachment to the scapula
If you take a look at the fascial connections (the different coloured lines on the dog below), you can see they all link to the hyoid. Again, this just highlights how issues with the hyoid can impact the posture and biomechanics of the WHOLE body. Addressing the hyoid can restore correct movement and balance in the dog.
Things to consider:
The hyoid apparatus is a very delicate structure, yet is subjected to constant stress and strain. It plays a part in many crucial roles; the movement and co-ordination of the head and neck, swallowing, breathing, panting, vocalisation and sniffing.
Common factors affecting the hyoid:
dental issues
a poorly fitted collar / harness / halti / muzzle
TMJ (temporomandibular joint) / jaw tension and asymmetry
trauma to the tongue
In terms of assessment, here are just a few examples of questions that may be asked to ascertain potential stressors:
Does your dog always walk on the same side, looking up at you?
Does your dog always lie curled up on the same side to go to sleep?
Does your dog carry sticks? Is this always on one side?
Does your dog repeatedly chew on toys?
Does your dog pull on the lead?
I hope this blog has given some insight into the hyoid and that you have either learnt something new or consolidated what you already know. Happy to answer any questions you may have or if you have any suggestions for more content, please get in touch!
Contact is welcomed via:
Instagram @helen_hactherapies
Facebook www.facebook.com/HACTherapies
E-mail helen@hac-therapies.co.uk
Mobile 07595 973057
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