11/07/2025
An important piece on biomechanics. Before subscribing into any theories, it is healthy to first ask a question: how much our interference does more harm than good?
The fleeting enigma of digital alignment
Since the first day an astute observer with an inquiring mind opened a hoof cadaver to testify to the hoof’s contents, no doubt the axis of the bones below the cannon bone came into view. We know these bones today as P3 (coffin bone) at the bottom and encapsulated by the hoof, P2 (short pastern bone) which forms the coffin joint with P3, and P1 (long pastern bone) which articulates with the cannon bone and together with the proximal sesamoid bones, form the fetlock joint. As a th*****me in either front or hind hooves, P3-P2-P1 (and the distal sesamoid or navicular bone) comprise the digit, or bones of the horse’s foot. The unique way in which these bones align gave rise to what farriers and others call the “digital axis,” or digital alignment, of the horse’s foot. This axis is less technically referred to as the “slope of the pastern,” and I believe most horse owners know it as such. Why bring all this up?
Because P3 is firmly encased within the hoof via its laminar attachments (stratum lamellatum), digital alignment has also come to mean the hoof’s toe angle should be the same angle as the digit (P3-P2-P1). As a young farrier in the 1970s I was told by other farriers senior to me and other authorities that this is a golden rule: toe angle and the slope of the pastern should align.
Indeed, farriers, veterinarians, anatomists, horse owners, horse trainers, and everyone who loves horses then all joined together in kumbaya relief, delight, and enlightenment as this God-given revelation became written into the textbooks of every equine hoof expert no doubt since Xenophon over two thousand years ago. Others went on to say further that the slope of the digit in front hooves should be parallel with the angle of the shoulder joint, and the hind digit parallel to the angle of the hip joint. No one dared to question the alignment mantra, even if they didn’t really know what it all meant, technically speaking.
Until Jaime Jackson emerged from wild horse country 40 years ago to say, “Hold on!
There is no evidence for this revelation in nature or in domestication, although it sounds good.” It’s not that I wanted to throw a wet blanket, I just noticed a crack in the logic that I felt needed more discussion.
If the joints are designed to hyperextend and “lock in place” during support, then surely they will form a hyperextended digital axis under the stabilizing reciprocations of the extensor and deep digital flexor tendons no matter what the angle of the toe wall. Or surely the digit will flex, collapse and send the horse falling on their knees and face. But to come to my main point, what should the toe angle of the hoof be for there to be a naturally angled digit? The very question I raised was sacrilegious, threatening ostracism, which I knew was coming anyway on the back of the newly emerging wild horse model.
But to be honest, this digit business is something I wondered about during my wild horse hoof research back in the BLM corrals during the early 1980s. While I measured toe angle, no radiographs were taken to give evidence of the digital axis. Thinking about it, to create a large enough sample to prove digital alignment would be a major radiographic undertaking. I’m unaware that this has happened, and getting permission to do it these days could very well be a problem. And the BLM is unlikely to do it either out of the kindness of their heart or the taxpayer’s good will. Nevertheless, I could say with much confidence that toe angles varied across Great Basin wild, free-roaming horses, but I could not say that toe angle equaled digital alignment without radiographic evidence.
So, that leaves us with domestication. And here things get very complicated, maybe worse than Rubik’s Cube, a composite of mini cubes, where the correct “alignment of cubes is one among 43 quintillion possible ones.” Why? Because no one can agree what that natural angle of the toe wall should be. Which raises a new set of annoying Rubik-like questions: Like, how would we get it to such a correct alignment anyway? And doesn’t it really depend on what we’ve done to the hoof under some other golden rule? Look across equestrian disciplines with their pet hoof care rules and you immediately see that problem. And what if the horse is shod, and how is it shod? What if the hoof is navicular, or laminitic, or wried, or the angle “doesn’t look right,” or no one is measuring, or no one cares, we are probably better off with Rubik’s Cube aren’t we?
The solution to this inscrutable, fleeting enigma of digital alignment, of course, is daunting. But let us assume that it is true, as surely it must be if there is such a thing, among America’s sound and healthy Great Basin horses. Then what? What the wild horse has taught me is that a naturally shaped hoof attached to a sound, healthy horse, is probably what that alignment is supposed to be. And so I came to a practical solution: it is the natural trim, a humane trimming method based on the Great Basin wild horse model embedded in the 4 Pillars of NHC, that is our vehicle to get us there, whatever that alignment may or may not be.
