Sunday, April 5, 2015

Steppin' Out: Hooves From An Artistic Perspective Part VIII: The Good Foot Part 2

Howdy! We're back again in this twelve part series exploring the equine foot in sculpture. As artists, we're free from many of the pressures inherent in the horse world, allowing us to advocate for this animal in ways often not afforded otherwise. So knowing how to make informed choices here lends authority and depth to our work. 

In this Part VIII then we're continuing with our analysis of a good foot in greater detail in order to duplicate it in our body of work. So let's get to it!

The Good Foot

Basically, the concept of a “good foot” is one that’s naturally balanced, adaptable and self-maintaining according to the conformation and lifestyle of the individual animal. However, this is a very different concept of “good” that has been historically used, with convention opting to define “good” by the hoof’s outward appearance, using idealized angles and lengths applied to every horse, in every situation. Yet, this is a static and rigid way of interpreting a structure that was designed to be malleable, adaptable and varied. Yet we’ll still find this kind of rigid thinking today, such as in the Strasser method or conventional method, and perhaps while applicable in certain situations, they may not be appropriate as blanket applications. 

Nonetheless, if a hoof didn’t conform to these ideal parameters, it was either dressed to match (often disregarding the internal foot), or simply deemed “a bad foot,” and dressed with various treatments to correct it. In other words, cosmetically creating a good foot would lead to good motion. While this may be true to a point (there is a symbiotic relationship between good feet and good motion), it appears that the amount of motion a horse enjoys has much more influence on the creation of a quality foot than the other way around. It also appears that what we see on the outside isn’t necessarily a good indication of what’s on the inside, since the developmental quality of the internal foot seems to be a dominant factor in good motion. Moreover, studies suggest that the totality of the animal’s management from birth plays a significant role in the adult quality of his feet.

All these elements have culminated in a radical shift in the concept of a “what is a good foot,” causing the entire industry to rethink, “What really is hoof conformation?” Thus, a new definition of foot conformation has emerged, and one based on the adaptability of the equine foot rather than what is ideal. In other words, when we look at a foot, what we’re actually looking at is the horse’s cumulative lifestyle at that moment, which is a radical rethinking of the equine foot, indeed. Dr. Robert Bowker expresses this new definition well in his paper The Growth and Adaptive Capabilities of the Hoof Wall and Sole: Functional Changes in Response to Stress (2003): 

This wide range of appearances of the hoof wall and the foot structures are commonly referred to as “conformation” of the horse. We define conformation of the foot as a “point in time” in which the structural appearance of the foot is a product of the environmental influences on the foot at the time that it is being examined. The structural appearance of the foot is continually being modified by the interactions of the foot with the environment and the environment’s influences on the foot and hoof wall. The term “environmental influences” includes just about everything that the horse has come into contact with since birth, including the extent of movement, ground surfaces, trimming and shoeing procedures or the lack of these practices, nutrition, etc. As a result, the conformation of the hoof and the foot can change when a horse is moved to a different environment and/or to living conditions different from those to which the horse was first exposed. The hoof wall and foot will then undergo additional adaptive changes and gradually become modified to the new environmental conditions. Therefore, the hoof wall and foot will have different morphological features than they did at the horse’s previous environment. An important concept for us as hoof care professionals is to begin to appreciate the significant influence that the environment has in determining the internal structure and the composition of the hoof wall and foot and to begin to apply these principles in the future.

This definition is very important for artists to consider because it means we cannot trust what we see as “correct” at any given time, especially when regarding feet within the domestic population. In fact, even some illustrations and pictures of good feet used in popular books on trimming and shoeing are actually pathological feet! Alarmingly, the feet of many horses in popular picture books are pathological, too, so an artist should take care. 

On the other hand, it also means that since there may be no one correct cookie-cutter on which to base our sculpted hooves, the “lifestyle” of our sculpture should be accounted for when sculpting the feet, which also can include seasonal changes and age. For instance, those horses living on rocky, hard terrain have feet that are quite different from those living in soft, marshy or sandy terrain. Or even more specific, feral horses in Nevada can have different feet from those living in northwestern Utah (Bowker, 2000). In this case, the feet of the Nevada population generally were slightly cupped with four points of contact, with prominent bars and a sole callus that reached to the apex of the frog. Their frog heels were large and prominent while the front part of their frogs were less developed (however, this area of the frog was tightly packed with dirt). In contrast, the Wyoming population lived on harder, more packed ground, resulting in more sole contact on the ground (a “flatter” sole), with more ground contact of the frog, bars and toe callus (due to the “filling in” effect discussed previously) (Bowker, 2000). The point being that these differences suggest that a foot may be adapted for one kind of environment, and so it may not be ideal for others. Thus, a sculpting philosophy that cannot account for the biological context of the subject is inherently flawed.

Nevertheless, unless feral concepts can be applied to domestic feet with similar predictability, the issue is rhetoricalbut, fortunately, it appears they can be. It’s been observed that barefoot domestic feet living in these conditions (and with adequate exercise) resemble their feral counterparts (Bowker, 2000) while feral horses captured and kept in a domestic situation rapidly develop typically flawed domestic feet (Ramey, 2005). These situations, among others, support the idea that applying feral foot concepts to domestic feet may not be wholly inappropriate. In most cases, the most appreciable difference (in which the frogs were usually wider in feral horses) was due to the amount of exercise: feral horses simply spend less time standing around than domestic horses. Dr. Bowker relates in his paper, Understanding the Feral Horse Foot (2000), “In radiographs of standing (but tranquilized) feral horses, the toe was short, while the coffin bone was raised slightly at its caudal part. The heel was very large. These observations are not unlike that of the ‘good-footed’ domestic horse!” 

There may be two additional commonalities between feral feet and sound domestic barefeet that challenge conventional theory: A short toe and a thick sole that supports weight. The former challenges the LT-LH trim while the latter discredits the idea that the sole shouldn’t bear weight (which is the job of the wall). Taken together with the previous ones, these commonalities imply that there may be a general, universal concept of what constitutes a good foot for all horses, in any discipline or lifestyle. Clearly, how this paradigm materializes will impact artwork. 

Accordingly, the definition of a “good foot” is ceasing to be described by specifics, but rather by the concept that a good foot is in a state of self-maintaining balance according to lifestyle. While this concept may seem over-simplified, achieving this in a domestic foot in typical management practices is a real challenge. To be more specific, because these details are relevant to artists, the hallmarks of a good foot are:  
  • It doesn’t entail just the hoof capsule, but the entirety of the internal and palmar foot. All these structures must be fully developed, healthy and work together efficiently. This means that evaluation of the foot must go beyond what’s seen on the outside, and go into and under the foot, too.
  • Management is a more powerful influence than genetics in creating and maintaining a good foot, especially during the formative first four years. Artistsbeware what you duplicate in sculpture!
  • It’s never static, but adaptable and reforms itself, externally and internally, structurally and biochemically, in response to the environment and the forces it experiences. Therefore, any evaluation should interpret a foot as a momentary “snap-shot.” In contrast, a bad foot is incapable of these adaptations to instead become unsound.
  • The equine foot becomes sounder the more it’s used, i.e. the more exercise a horse gets on the proper surfaces, the better the foot becomes. Horses weren’t designed for a sedentary lifestyle.
  • A good foot is naturally balanced and finely tuned to the horse’s lifestyle, which can create forms that run counter to what convention believes is “good.” 
  • Of adequate size to support the mass of the animal and the forces it encounters.
In a nutshell, a good foot is the sum of all its parts. It also means that each horse has “custom made clogs,” which is an important detail for sculpture. For example, our sculpture of a Camarque Horse should have very different feet from our Mustang living in the Oregon desert. Or, more specifically, our domestic horse sculpture "kept on" moist pasture should have different feet from a domestic horse kept on a dry lot. 

Another important point to remember, too, is that all horses are born with hoof components of the same quality (barring a birth defect or breeding decisions that don’t select for a quality foot). The feet only develop into forms that are optimal or pathological based on management. As expected, this situation creates a heap of caveats for an artist looking to life study or reference photos for guidance. 


As discussed perviously, foals have very different feet from adults because they are “blank slates” (only in the fetal and newborn state are the hoof wall structures similar in their cellular composition). It’s not until a newborn’s feet experience the elements and physical forces that they begin to adopt the familiar round forefoot and pointed hindfoot shapes. More importantly, they also begin to change structurally on a cellular level; the cellular composition of the toe, quarters, heels, sole and frog change, depending on the variable forces visited on each region. Specifically, the primary epidermal laminae in the fetus and newborn have a uniform distribution around the hoof wall in both the hindfeet and forefeet (Bowker, 2003). Yet within just a few days after birth, significant cellular changes begin, based on the stresses the hoof encounters.

For instance, the primary epidermal laminae become more developed in the forefoot than the hindfoot, and become morphologically different in number, shape and size along the different regions of the wall (Bowker, 2003). In older foals (6 months–1 year), the morphological changes are more pronounced, and the density of the primary epidermal laminae increases at the toe, but lowers in the quarters (Bowker, 2003). As we've already learned, the internal foot undergoes some significant changes, as well.

Over the developmental years of a young horse, these morphological changes in the foot continue and adapt to the animal’s lifestyle, which is how early management has such a powerful influence on long-term soundness. In particular, the first four months seem to be an important window in developing a quality foot insofar as a foal’s feet need adequate exercise and abrasive, firm terrain to stress the foot appropriately, internally and externally, especially for creating sole pressure. If these conditions aren’t present, a foal’s feet tend to contract and can fail to reach their proper size (Love, 1998), while the internal structures may fail to mature (Bowker, 2003), leaving the animal with inadequate means to support himself in adulthood. In other words, a developing horse’s foot requires stress and abrasion to develop properly. This situation not only serves as a caveat for stable managers, but also for artistswe should be aware of how a foal is managed before using him as a straight reference when sculpting foal feet, and we should be aware of how a foal foot changes during the first days after birth to recreate appropriate critical details. 

Additionally, as we learned previously, foal feet vary in terms of angle, from about 50˚ to 70˚ in the forefeet, though 60˚ - 65˚ is most common (and preferable). An angle lower than 50˚ may indicate flexor flaccidity while an angle higher than 70˚ may indicate a clubfoot. However, don’t confuse the foal’s hoof sulcus (at about 10 weeks old) with a broken axis. 

Anyway, now that we have all this to chew on, let's make some specific value judgements on the equine foot only because we have to have something to go on when we sculpt!

The Bony Column

A good foot doesn’t start on the outside, but on the inside. For the purposes of this series then, we’ll deal only with the coffin bone, though the 1st and 2nd phalanges usually are considered part of the foot, too.

Now there’s debate as to whether the coffin bone should be parallel to the ground at stance, or elevated slightly by about 3˚- 5˚ in the posterior. Radiographs of feral and sound domestic feet offer sound examples of both these possibilities, so the situation is still unclear, particularly when these two camps may be talking about the same situation, but in different ways (as previously discussed). 

At any rate, the simplest way to think of the bony column and the hoof capsule together is as a lever system that facilitates efficiency of motion and the mechanical integrity of the foot. In a foot with natural proportions, breakover is made more efficient by minimizing the leverage (or pull) on the hoof capsule and coffin bone through a phalangeal lever that’s as short as possible. 

This phalangeal lever is comprised of the 1st, 2nd and 3rd phalanges, with the ground as the fulcrum and breakover as the pivot point. A phalangeal lever therefore can be different lengths: levers comprised of a sloping bony column and a long toe have a longer lever, while those comprised of a more upright bony column and a short toe have a shorter lever. In short, a long-toed foot has a longer lever than a short-toed foot. The horse with a shorter lever uses less energy for breakover than a horse with a longer lever, translating into reduced fatigue and fatigue-related injury. Additionally, the longer the phalangeal lever, the longer breakover is delayed, resulting in a tendency for toe-first landings, interference, clumsy movement, unnatural stress on the navicular area and flexor tendons (especially the deep digital flexor) and the suspensory ligament, and bruising on the tip of the coffin bone (pedal osteitis), all culminating in a slew of pathologies (discussed later).

According to observation and biomechanical studies, it appears the horse was meant to move with a short phalengeal lever. It has been proven repeatedly in radiographs that abnormal phalangeal alignment is returned to natural angluation the closer breakover is placed towards the anterior tip of the coffin bone, about 1/4” from the tip (paired with frog and bar support) (Page, et al., 1999). Not coincidentally, these are within the same parameters found in feral feet. 

Likewise, the work of Dave Duckett FWCF regarding the relationship between the bony column and the outside of the foot has proven reliable in this regard, and even confirmed through the research of Doug Leach DVM with load sensors attached to the hoof. Additionally, his alignments identify two important hubs within the foot by recognizing that as the foot moves and loads, its static center of gravity changes. The first hub is the center of weight bearing on a fully loaded foot, the Duckett’s Dot, or the center of the coffin bone. The Dot is the one reference point on the bottom of the foot that never changes, no matter how badly the foot distorts (due to the nature of the anatomical attachment of the sensitive frog). It’s also the only external landmark that identifies the center of the coffin bone through measurement. The second hub is Duckett’s Bridge, or the center of articulation of the coffin joint, and also the mechanical center of the foot. These two landmarks can help an artist place the hoof capsule and solar structures correctly on the bony column of her sculptures, rather than guessing and risk creating a pathological foot. 

The alignment of the bony column is of critical importance for soundness, regardless of the actual angle. These alignments should manifest as follows:
  • The 1st, 2nd and 3rd phalanges should line up in the same angle, from the side and from the front. 
  • A line through the rotation of the joints should go through the point of breakover (Figure A). 
  • A perpendicular line dropped from the Bridge should bisect the weight-bearing surface of the foot (Williams and Deacon, 2002). 
  • The dorsal wall of the hoof capsule should mirror the dorsal wall of the coffin bone, and they should be lashed tightly together. However, this parallel, tight alignment cannot always be assumed in domestic horses because of the LT-LH trim and white line disease (Lind).
  • The top of the hoof capsule should attach at, or just below, the extensor process of the coffin bone. This also cannot be assumed in the domestic horse due to the prevalence of "mechanical sinkers," a condition nonexistent in feral or sound domestic feet.

Deviations in the bony alignment predispose the foot to unsoundness, and should be avoided in sculpture. Some common deviations are:
  • Broken-back axis or spade toe: Characteristic of a LT-LH structure (long toe-low heel), which is responsible for most structural lameness more than any other misalignment (not to be confused with the natural coordination of the foot when a limb is placed under the body).
  • Broken-forward axis or clubfoot: Subjects the foot and limb to increased concussion and injury and can produce choppy gaits. It also inhibits the necessary mechanics of the foot. They vary in severity and can be be congenital and caused by conformational misalignments, or by misguided farriery, injury, over-nutrition or contracted tendons. Contracted tendons are caused when the perforans tendon tightens and pulls the heel up and the toe back. It can affect one or both feet, and most commonly occurs on the forefeet.
  • Coon foot: Characterized by a pastern angle less than the hoof angle, and often associated with pasterns that are too long and sloping, being “run down” (a spraining or tearing of the suspensory ligament), DSLD or ESAD. While this structure appears to produce a smooth, springy gait, it’s actually quite weak and prone to lameness, and also prone to underrun heels and a LT-LH structure.
  • Toe In: If conformational, the deviation begins in the shoulder and becomes most pronounced in the fetlock, usually leading to uneven wear and interference. (Note: It’s said by some that a slight toe-in stance is desirable by “freeing” the elbows for more scope in motion, often found in Iberians for this reason.)
  • Toe Out: The same as toe-in, only in the opposite direction.
  • Broken In: This deviation begins at the joint between the 2nd and 3rd phalanx, skewing the hoof capsule inward.
  • Broken Out: The same as being broken-in, only in the opposite direction. 
  • Offset Axis: From the front, the bony column is offset to the alignment of the hoof capsule, usually leading to lameness or injury by shifting the weight-bearing surface of the foot out from under the center of the limb, resulting in uneven wear and function. 
Artistic Mistakes 
A broken axis is common in artwork, usually of the Broken-back or coon-footed variety—many artist mistakenly create sculptures depicting DSLD or ESAD for this reason. Offset axis is particularly common since artists sometimes misinterpret the capabilities of the phalangeal joints, or don't understand how the hoof capsule should be centered on the bony column. Broken In and Broken Out axis also are seen, though less commonly. [Note: A Broken-back axis shouldn't be confused with the natural coordination of the foot at stance. For instance, when a horse has his leg extended backwards, it's normal for the foot to stay level with the ground, but for the phalanges to rotate forwards to accommodate.]

Internal Foot

Although not directly applicable to sculpture, knowing about the internal foot can guide the sculpting of our external foot. Just like a good real foot is built from the inside out, so is a sculpted foot!

Basically, the internal foot entails the lateral cartilages, the digital cushion, the laminae, the various coriums, the arteries and veins, ligaments, tendons, and the arterio-venus capillary complexes.

The internal foot, especially the digital cushion and lateral cartilages (along with the frog and bars), not only functions to support the horse and dissipate impact energies, but also works as a blood pump. The primary pathway for blood comes down the back of the leg to the heel, then forward to the toe. Blood is pumped through the arterio-venus systems with each step when the foot is loaded and distorted, which then snaps back into shape at breakover, like a pumping heart. This implies the frog shouldn’t only touch the ground when the foot is loaded, but also be of the correct structure and quality in order to participate in loading properly (Henneman).

A quality internal foot currently is described as:
  • A large, thick digital cushion made of stiff, dense fibro-cartilage that lies directly over the bars. 
  • Laminae that are healthy and closely-knit with their cornified pairs, and not made to bear weight. The laminae “leaves” should be low in number and large, too. 
  • Coriums that should have their full integrity in order to grow their respective horny counterparts, and function as part of the energy dissipation mechanism within the foot. 
  • Ample blood vessels and dense capillary systems. Bowker found that good feet have more blood vessels and denser capillary systems in their lateral cartilages than those feet with soundness problems (Bowker, 2003). For instance, in those feet with thick, developed lateral cartilages, the number of vascular channels around the navicular bone exceeded 25-30 channels per two lateral cartilages, whereas bad feet have no such vascular channels, or only 3–5 per two lateral cartilages (Bowker, 2003). After about 4–5 years of age, these physical changes begin to occur in the digital cushion, lateral cartilages and capillary bundles in all horses with proper stimulation. However, Arabians and Standardbreds were found to have a higher percentage of fibro-cartilage in the digital cushion and thicker lateral cartilages at an earlier age (Bowker, 2003). 
A poor quality internal foot currently is described as:
  • A digital cushion comprised of fatty, soft connective tissue, more like a thin sheet rather than a dense, thick pad. Interestingly, Bowker found a strong link between navicular syndrome and the lack of fibro-cartilage in the digital cushion (Bowker, 2003). It’s believed a weak digital cushion cannot protect the navicular area from the impact energies it was never designed to withstand. 
  • Small, thin lateral cartilages, also implicated in navicular syndrome (Bowker, 2003). Inadequate lateral cartilages usually mean underdeveloped capillary complexes that can inhibit circulation and energy dissipation within the foot. 
  • Damaged coriums and laminae that can compromise the growth of essential structures or the integrity of the internal foot.
Palmar Foot

Of particular importance to both the foot and artists is the distal surface of the foot, often referred to as the “palmar foot.” It entails the sensory detectors, heels, bars, frog, sole, white line, water line and the distal border of the wall (internally, it also includes the navicular area, distal surface of the coffin bone, distal coriums, the digital cushion and the lateral cartilages). 

These parts don’t function individually, but together as a system to facilitate energy dissipation, circulation, and the recycling of impact energies into propulsion. This means a quality foot cannot be sculpted without an understanding of the separate parts and also how they work together. Sculptural errors created in the palmar foot can indicate unsound feet because the palmar and internal foot are closely married in both function and symptomatic qualities. In this regard, we can “judge a book by its cover!” Conversely, a fully developed internal and external foot produces a rather specific type of palmar foot (which we'll get to later) which artists should be able to recognize in order to recreate it for sculpture.

Of particular note to artistsdon’t be afraid to sculpt in “solar plugs” of mud or caked material on either barefoot or shod sculptures. Feral studies have found that packed mud on the distal surface helps to ease peripheral loading in those feet with deep vaults which are in transition to flat, packed terrain. Interestingly, the lips of the frog may be designed specifically to trap mud and hold onto a solar plug to help with foot mechanics in specific habitats (Love, 1998). Some shoemakers even design their shoes to maximize the retention of mud beneath the sole (such as the Natural Balance Shoe®), and some natural hoof care practitioners endorse leaving caked material on the underside of the foot before riding, scraping it to be level with the shoe (if shod) or wall (if barefoot) (Love, 1998). Curiously, thrush appears to be absent in feral feet despite often being caked with mud, and it's believed the tissues are so thick and healthy due to proper stimulation (i.e. densely calloused) that fungus or other infections cannot take hold (Love, 1998). In contrast, the soft, fleshy, aggressively trimmed and underdeveloped solar tissues of the domestic horse, who often must stand around in a stall of soft, soiled material, too, usually fail to keep thrush at bay.

A quality palmar foot can be described as follows:
  • For most quality feet, the widest part of the foot is about 1 inch-3/4 inch behind the frog apex, or at the termination of the bars, right about where Duckett’s Bridge is located. 
  • The distal solar surface can be highly polished and smooth, or can exhibit its natural exfoliation process, depending on the individual’s lifestyle. 
  • Each of the palmar components should be fully developed.
A poor quality palmar foot usually has these symptoms:
  • Underdevelopment in any one or more of the components that comprise the palmar foot (discussed in detail later). For example, a foot lacking a developed digital cushion and lateral cartilages tends to have contracted heels and underdeveloped frogs (Bowker, 2003) while “sinkers” usually have flat soles (or shallow collateral grooves), which lack the natural concavity of the solar surface that mirrors the distal surface of the coffin bone (Ramey, 2006).
  • Asymmetrical development, which skews the foot away from being naturally balanced.
Artistic Mistakes 
The palmar foot often is treated hastily in artwork, leading to errors and malformations (discussed in more detail later), all of which indicate unsound feet. Sculpting palmar feet shouldn't be an afterthought.

Sum Up

Phew! So now that we're making value judgments, we'll continue to explore the rest of the foot in the next installment. Meanwhile, keep hoofin' it in the studio!


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