Functional Anatomy of the Equine Hoof

It occurred to me this morning, as I'm reading various hoof-help posts, that owners and many hoofcare practitioners have little understanding of what compromises the functional anatomy of the horse's hoof. Without going into great detail I want to simply outline the basics of how the horse's hoof is structured. I've written before about the various parts of the hoof and their function. You can read various short articles and see videos right here on Scoot Boots ... simply go to the Blog posts

First, let's all get on the same page as to the parts of the hoof:

Understanding the parts of the hoof, being able to label the pertinent parts and understand their functioning is imperative in order to understand what constitutes "healthy" hooves. I've written before about the intricate parts of the equine hoof and what their detailed functions are so here I will briefly go over the base points so everyone has at least a solid knowledge of the parts and their base function.

We'll start with the HEEL BUTTRESS ... also known as the Heel Platform.

The heel is really the foundation for the entire hoof. Without a solid heel there is "no hoof". The HEEL BUTTRESS is the "platform" upon which the hoof lands and without a solid landing platform the rest of the hoof simply cannot function properly and, more so, can be irreversibly damaged. The HEEL BUTTRESS extends into the foot to form a solid 'buttress'.

Directly underneath the Seat of Corn at the Heel Buttress there should be a good inch of collateral groove depth. Looking from the back of the hoof there should be around 2 inches from ground to hairline. The hairline in the back of the hoof should be almost straight across the heel bulbs without an exaggerated "W" shape.

SOLE: the SOLE is the protector of the coffin bone (P3; Third Phalanx). It should be a minimum of 1/2" thick. It is thinnest right at the APEX and this portion of hoof should never be touched unless exfoliating and can be peeled off with fingers. (There are exceptions but too lengthy to go into in this post.)

BAR:  the BARS of the hoof are to provide traction, support for the back of the hoof preventing the hoof from over-expanding during landing and as 'skid brakes'. They are NEVER to be 'dug out' but, rather, "skimmed" down to sole level. Some protrusion of the bars is actually favorable in wet or slippery conditions so even 'skimming down to sole level' may not be the best trimming. On the contrary, never should they be allowed to get so overgrown that they are folded over forming another layer of horn over the sole.

WHITE LINE:  The WHITE LINE of the hoof is the yellowish line around the hoof wall that connects the wall of the hoof capsule to the inner foot. This area should be solid without any separation so that dirt, mud and environmental insults are not allowed into the foot. Trimming the hoof should respect the WHITE LINE where the toes are never brought back further than 1/2 way through the WHITE LINE. The outside distal edge of the white line is non-sensitive but the inner 1/2 of the white line is sensitive. Taking back the toes so much that it insults the white line can cause lameness much as if you were to cut back your toenails too much and 'quick' your nail.

TOES:  The TOE of the hoof should be short enough that the break-over during lifting of the hoof from the ground is quick and does not 'drag' on the toe.  The toes help to protect the inner foot and the circumflex artery that runs around the distal edge of the coffin bone.

The breakover of the toe should be from 10 o'clock to 2 o'clock in position while looking at the bottom of the hoof with the toe being 12 o'clock. It's about 1 inch from the distal edge of the toe back towards the apex. The callused area from 10 o'clock to 2 o'clock is known as the "toe callus".

WALLS:  The walls of the horse's hoof should be smooth, a bit shiny and be free of any prominent rings. They also should not exhibit any cracks, chips or flaring. Of course, the walls protect the entire foot inside the capsule and should be of uniform thickness, about 1/2" thick, corresponding with the thickness of the sole of the hoof.

On the bottom (solar view) of the hoof there should be a nice SOLE CALLUS that runs from heel to heel which actually forms a 'natural' horseshoe. This area, the SOLE CALLUS, comprises about an inch of area from the distal edge of the hoof wall to just inside the white line and includes the white line. This is the main weight-bearing portion of the hoof. The walls should not protrude further than this callused area but form a nice, solid area on which the hoof lands.

FROG:  The FROG of the hoof is a major functioning part of hoof health. It is the shock absorber as well as the energy dissipator of the hoof.

The frog is a dynamic part of the hoof that changes in response to terrain and other hoof demands. The frog's width should be approximately 50 to 60% of its length, and the portion closest to the apex should be substantial enough to touch the ground when the horse is bearing weight. If the frog is not touching the ground during hoof loading then the rear of the hoof will not be able to be developed properly and will be weak.

The FROG has a CENTRAL SULCUS that should be just a small indent about the size of a thumb. There should be NO CRACKS indicating infection and/or contracted heels. This can predispose the horse to lameness if not addressed correctly.

HAIRLINE: Coronary band.   The HAIRLINE/CORONARY BAND is a malleable band of tissue and hair that is responsible for growing new hoof. It takes about 8 months to a year for a completely new hoof to grow from the HAIRLINE/CORONARY BAND down to the ground. A normal coronary band angle is considered to be about 20° to 25°; if the coronary band/hairline angle is greater than 30°, the horse probably has an extremely low or negative palmar/plantar angle (the angle the bottom of the coffin bone makes with the ground.) Simply put, negative palmar/plantar angles mean the horse’s heel is being crushed as is the rest of the foot inside the capsule. The HAIRLINE should be smooth and straight with no dips or curves in it. When looking to the front of the hoof the line the hairline makes should be parallel with the level ground. When looking at the back of the hoof, the hairline should also be almost straight and should not be touching the ground when the horse is static.

While there is much more detail that goes into ascertaining a healthy hoof, this will give a good base from which to study further if desired. It would be prudent to also learn the bones, tendons, ligaments and cartilages inside the hoof capsule along with those of the lower limb to fully understand just how a horse's hoof works and in what form it should be for optimal health.

COLLATERAL GROOVES/SULCI:  COLLATERAL GROOVES of the hoof should range between 2/3 in and 1 1/4 inch deep from apex to heel. They should be clean and free of Thrush. Under the apex the collateral groove should be about 10-15 milliliters deep (about 2/3 in) as the coffin bone sits just on top of the apex at about 1/2" in the foot. A more shallow COLLATERAL GROOVE at this point could indicate thin soles which is going to cause the foot not to be adequately protected from environmental insults. Any less than 1" depth at the back of the foot, under the seat of corn, indicates low heels. Low heels and thin soles are indicative of hoof collapse causing lameness.

These are just some of the points of which to be aware when assessing hooves for health. Not all hooves are created equal and there will be variations, even on the same horse, that will not affect the soundness of the horse. On the other hand, a slight deviation from the common factors can cause a more sensitive horse to become lame. So it's important to become familiar with the parts of the hoof. As always, no hoof-no horse.



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Gwen Santagate is the author of "10 Secrets to Healthy Hooves" . 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 keeps a small herd of her own equines and continues to offer consults for horses in need.