Navicular Revisited

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Good Day to Y'all! 

This week it's appropriate to go over that dreaded state of the hooves ... NAVICULAR.

I know I've posted before on Navicular but it seems that there is a rampant increase in diagnoses of this situation.

So, let's revisit it afresh.

 First of all ... let's determine just what the name "Navicular" means when a vet says, "Your horse has Navicular!"

In more cases than not, it simply means the horse is sore in the back of the hooves for some reason that is unidentified. That is NAVICULAR *SYNDROME*. Navicular *Disease* is a bit more serious and demands its own attention.

Navicular disease in horses is a progressive degenerative condition involving the navicular bone (which is located behind the coffin bone in the hoof), the bursa and the deep digital flexor tendon (DDFT) of one or, more commonly, both front feet.

*Navicular* is not actually a 'disease', it is a syndrome of abnormalities.

For this article's purpose we will look expressly at "Navicular *Syndrome*" 

So, again, Navicular means palmer heel discomfort of unknown cause. Palmer meaning "back of" the front hooves. Discomfort can range from the slightest bit of feeling "off" around the corners of a ride or down and out head-bobbing lame at all gaits.

First off, what is the NAVICULAR bone anyway?


In the illustration you can see the Navicular bone in the heel of the hoof ... it is the smallest bone in the foot yet gets the most 'action' of loading of the hoof! The Deep Digital Flexor Tendon (DDFT) runs across the Navicular bone and the bone acts as a fulcrum for that tendon. The bone is protected by a fluid filled Bursa and supported in place by the Impar Ligament. Damage to the DDFT or the Bursa or the Impar Ligament can cause discomfort or full-blown pain in the horses foot. If the navicular bone is displaced at all, due to imbalances of the foot and hoof, that can also cause discomfort. The horse will want to land toe-first in the attempt to avoid the pain of a heel-first landing.

Clinical symptoms of "Navicular" include:

  • Unilateral or bilateral lameness of the forelimb
  • Sensitivity to the hoof testers when applied to the frog or heel
  • Lameness improves with palmar digital nerve anesthesia.

LAYMEN'S observations might be:

  • Intermittent lameness.
  • Chronic lameness.
  • Bilateral disease affects.
  • Shortened stride.
  • Poorly balanced feet.
  • Stumbling when ridden.
  • Digital vessels palpably enlarged.
  • "Pointing" of one front foot or the other
  • Navicular syndrome pain often gets more severe with work and less severe with rest.

So, what to do with this information?

If your horse is exhibiting any navicular symptoms then it is imperative to get to the root cause and eliminate that cause of the symptoms.

Sometimes that involves a bit of sleuthing.

The most common cause of Navicular is imbalanced trimming/state of the hooves. Because of the imbalanced trim, the horse cannot stride out in comfort and will compensate for the discomfort causing further motility issues.



(Image courtesy of American Farriers Journal)

Low under run heels, long toe syndrome is a MAJOR cause of "Navicular". On the other hand, disease of the frog and heels can cause 'navicular' as well. Unattended Thrush that is allowed to proliferate will eat right into the foot and, eventually, the bone - including the navicular bone. This is where the simple 'Navicular Syndrome" can easily turn into Navicular Disease! Repetitive concussive force on the hooves, such as that from galloping frequently on hard, packed surfaces, can cause "navicular". Interference with the blood supply or trauma to the bone can cause navicular. Confinement can also be a cause of navicular. High weight bearing bars are a major contributor to caudal heel pain, which is often falsely diagnosed as Navicular.

Dr. Robert Bowker states, "From my studies, I’ve been led to believe that it’s our husbandry practices–the way we care for our horses–that have created navicular disease.  Essentially, navicular disease comes down to vibrations; vibrations destroy tissue in the foot. 
How does this happen?  When horses are made to live on or if they are worked continuously on hard surfaces, the frequency of the vibrations increases.  Even vibrations as low as 250-300 Hz can destroy connective tissue, but it’s been shown that horses stopping on hard ground can undergo vibrations up to 3000 Hz.  My belief that hard surfaces, shoes, our husbandry practices, and our methods of trimming or shoeing are the main culprits for these increased impacts/vibrations upon the feet. 
Shoes also increase the frequency of vibrations in the foot.  Tissues can only absorb so much energy before the bones then start to deteriorate.  One study, from 1988-89 performed in the Netherlands, showed that horse shoes can increase the vibrations up to 2500 Hz.  So yes, shoes play a definite role in the development of navicular.  But having said that, even a barefoot horse living or working on hard surfaces can develop navicular. "


(Original photo Pete Ramey) Here you can clearly see the heel buttress extending up into the rear of the hoof 'cradling' the digital cushion and rear of the hoof. You can also see the nice thick sole.

In my own observations I have to say that I agree with Dr. Bowker's statement concerning 'vibrations'.  When heels are continually trimmed too low then the heel buttress inside the foot is also trimmed down so the digital cushion begins to thin and slip down around the back of the foot. The frog is also thinned as the heels get lower and lower until it is basically ineffective in its shock absorbency. The digital cushion begins to deteriorate to become more fatty in its makeup than fibrocartilagenous (strong, cartilage-like fibrous tissue) and, as such, the entire shock absorbing system of the hooves becomes ineffective. This means that the concussive shock of constant pounding during movement is destroying the tissues in the foot (never mind the legs as well) and, as a result, the vibrational impact increases in the hoof and lower limb (and the rest of the body too) ... so that the horse become 'Navicular'. And yes, steel shoes increase the vibrational impact on the hooves and lower limbs. So now - just imagine the damages being cause from imbalanced and improperly trimmed hooves that are then clad in shoes ...

What a mixture for disaster!  So sad for the horses who are so stoic to put up with all of this mess!

Well, I'm sure you get the idea, by now, what Navicular means, how its caused and then, logically determining what needs to be done to correct the situation.

CORRECT TRIMMING is ESSENTIAL for healthy hooves. And beyond that ... don't panic if you hear the word "Navicular" out of your vet's mouth -- stay calm and do some assessment of the situation.

What can YOU do to remediate it? 

Find a GOOD hoof-care Practitioner who really understands the Equine Foot and how to correctly TRIM the hoof-in-hand on the horse-in-hand.

With that I'll say EDUCATE YOURSELF on what constitutes healthy hooves. Find out what the workings of healthy hooves are (anatomy & physiology of the equine digit and lower limb) and see to it that your trimmer understands the importance of it as well.

If you don't know where to begin, just ask me.  I'm around and I'd be more than happy to help you out.

I've been there, done that and have spend decades 'fixing' those horses deemed to be "Navicular". 

Ya just gotta have the know-how or find someone who does.

Education, Folks. It's all about educating yourselves and making sure your hoofcare provider is educated as well.

Hope this has been helpful to you. 

See you next time.

 

Gwenyth Browning Jones Santagate is the world-renown author of "10 Secrets to Healthy Hooves" and "Natural Hoof Anthology" as well as a noted author for various international equine publications including The Horses Hoof, Equine Wellness, Natural Horse Planet as well as a contributing author for the 2001 United States Federal Mounted Border Patrol Training Manual. For the last 37+ years, she has maintained healthy hooves with natural trimming on thousands of horses and specialized in pathological rehabilitation hoofcare for the last 18 years. She and her husband John keep a small herd of their own equine in NE Connecticut and continue to offer consults for horses in need. For further information please click here:  www.thepenzancehorse.com

Gwenyth is available for freelance assignments, contract work and consulting.

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