Underrun Heels & What To Do About Them
©2012 Doug Butler PhD, CJF, FWCF
Butler Professional Farrier School, Crawford, Nebraska 69339
Underrun heels are a common problem in today’s performance horses.

Underrun heels are defined as heels where the angle of the hoof heels is less than that of the hoof toe when viewed from the side. Some clinicians have defined them by saying the heels become underrun when they are more than five degrees less than the toe. The horn tubules may be bent forward at the bottom and the pastern is often steeper than the hoof angle. Underrun heels are known to predispose horses to navicular disease, low ringbone and quarter cracks.

Genetics is the primary cause
Underrun heels, also called sloping or collapsed heels resulting from the “long toe, low heel” syndrome, are highly heritable (easily passed on to offspring). They are found in many, and even most, of our modern performance horses. Some estimates put the heritability of this condition as high as 75 percent, with 25 percent due to the environment, such as neglect, use, nutrition or inaccurate farrier work.

The condition is more prevalent today due to the fact that over the past 50 or 60 years we have selected horses for factors other than sound feet and legs. Over selection for disposition, color, height and size, as well as cow sense, jumping ability and speed, have contributed to the problem. Occasionally, you will hear a horseman say that in the last half-century we have “bred the feet off of our horses.” In effect, we have created an animal with “a hot rod motor in a tin can chassis.”

Often, susceptibility to such debilitating conditions is most prevalent in specific families. For example, susceptibility to colic and club foot is known to be most prevalent in specific Arabian horse families. Hyperkalemic periodic paralysis (HYPP) is specifically confined to one family of Quarter Horses. And, degenerative suspensory ligament desmitis is most common in Paso Fino horse families.

Geneticists sometimes call inherited unsoundnesses “partial lethals” because they tend to reduce the life expectancy of offspring from animals who display the trait(s). Ideally, the more successful breeders select against these partial lethals. Some of these traits, whether dominant or recessive, are linked to desirable traits such as cow sense, jumping or racing ability.

Other factors include neglect, use
Although genetics is the primary cause of underrun heels, there are many other contributing factors. Neglect of a horse’s feet that have the so-called “long-toe, low-heel” conformation is a big factor. These feet must be trimmed frequently and the toes dressed back to keep them sound. Farriers often are blamed for this problem when it rarely is their fault. The horse owner is responsible for frequently scheduled hoof maintenance.

Horses with the long toe, low heel conformation require more frequent maintenance than horses with ideal hoof angles of 52 to 57 degrees (average 55). Studies in France by Barrey have shown that horses with steeper angled hooves are more likely to remain sound.

The use of the horse is a contributing factor to underrun heels. Horses that run hard over unyielding surfaces pound the heels. At the faster gaits, the heels hit first and take the shock of the horse’s weight. Horses that are asked to jump fences pound or jam their heels when landing. Poorly conformed feet with weak laminar attachments that are so common in many Warmblood sport horses make this problem worse. Reining horses that stop hard also stress their heels excessively. However, there seems to be a correlation between underrun heels and tractability for cow working , jumping, dressage and speed events.

Shoe fit is critical
Shoes should be fit with the heels ending at the point where a line from the bulb or “origin of growth” to the ground is parallel to the dorsal hoof wall. The dressed dorsal hoof wall should be parallel to the dorsal surface of the coffin bone. This often means fitting the heels of the shoe behind the buttresses to the widest point of the triangular frog.

Fitting shoe heels longer than what is reasonable to support the leg may create forces that can make the problem worse. Shoeing too short, in an effort to prevent lost shoes, may also create destructive forces on the foot. Quarter cracks may occur as the foot rocks back and downward forces tear open the coronary band. Wet environmental conditions can weaken sloping heels and make it more difficult for the horse to retain shoes.

When the hoof tubules are straight and strong, they will remain parallel to the toe even when a wedge is used to raise the heels to align the pastern angle. If the hoof tubules are weak and bent at the bottom, raising the heel with a wedge is not appropriate as it can cause the heels to further crush. In this case a heart bar shoe, which temporarily transfers the weight off the heels on to the frog, will allow the heels to grow.

Trimming the hoof heels may be necessary to remove old growth containing the externally visible bent tubules. However, the hoof heels must be raised back up by a wedge(s) to relieve stress on the internal structures of the foot that may be damaged by a low hoof angle. In any case, the underrun heels are not going to go away, they can only be accommodated by a skilled farrier. Reduction of stress by aligning the hoof axis with the pastern axis is critical. When the hoof/pastern axis is aligned, the least amount of stress is present in the leg, according to research by Balch and others.

Avoid solutions that ignore limb biomechanics
Fad farriery that includes one-size-fits-all shoeing for every horse, such as “cutting the heels to widest part of the frog” and making the “base of the coffin bone parallel to the ground,” ignores the biomechanics of the skeleton.

Shortening the hoof base by using a smaller size shoe, and then pulling the shoe back to make it fit, increases the concussion in the foot by as much as twenty percent and thus increases the chance of internal foot injury according to Balch and others.

An experiment conducted in England by Dyson and others determined that for every degree the angle of the distal phalanx bone (coffin bone) was raised, the stress on the navicular bone was reduced by 4 percent.

The justification for fad farrier practices is often given as a “natural solution.” This implies that wild horses have a desirable type of foot and therefore we should select trimming and shoeing methods based upon the shape and appearance of wild feet. Keep in mind that wild horses don’t have square feet and don’t wear shoes. Your horse is an over-selected domestic horse – not a wild horse.
Underrun heels are going to continue to be a problem. It has taken a long time to breed them into our horse populations and they seem to be related to characteristics we consider desirable in our horses. They cannot be “fixed” --even by expert farriers.

The most practical solution for this problem is to maintain horses at a balanced and comfortable pastern angle by regularly employing a competent well-trained farrier. One that is capable of advising you on what type of trimming and shoeing will best maintain your individual horse(s) for its intended use.

For detailed information, photos and case studies of underrun heels and how to create geometric balance necessary for optimum horse foot function, see pages 71-101 in The Principles of Horseshoeing (P3). Visit our website at www.dougbutler.com for more information on this ultimate reference manual for horse foot care.

Attention Practicing Farriers – If you want to boost your efficiency by up to 30 percent, learn or refine a particular skill, or find out how to grow a more profitable business, we can customize a training program just for you at our upcoming “Practicing Farrier Workshop” on December 7-11, 2009 at our training facility near Chadron, Nebraska. For more information call Jake at 800-728-3826 (press 3). Call today to discuss your particular needs and plan now to attend this rewarding and enriching training to grow your professional skills.


Doug Butler has a PhD in Equine Science, is an AFA Certified Journeyman Farrier and a Fellow of the Worshipful Company of Farriers of Great Britain. He has taught farrier science and craftsmanship at several universities, including Colorado State University. He now offers farrier training through his publications and a private farrier school. Information can be obtained from his web sites www.dougbutler.com and www.butlerprofessionalfarrierschool.com.

Contact: Butler Professional Farrier School
495 Table Road
Crawford, Nebraska 69339
Phone: 800-728-3826 or 308-665-1510
Email: info@butlerprofessionalfarrierschool.com
Website: butlerprofessionalfarrierschool

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