Your horse moves so smoothly that you always pause, just to watch and admire her – head held high, mane flowing, little puffs of dust from under her feet with every step – she makes you want to be on her back, enjoying the ride. And she makes it look so easy, you rarely think about what's going on in that beautiful body, moving her 1,000 pounds so effortlessly. This is just a tip of our hat to those moveable parts – especially those feet! They sustain and support all of that half-ton of weight with every step she takes, and they rarely have a complaint – and so we tend to take them for granted. But they are probably the finest shock absorbers your horse's Maker ever designed. Join me as we consider what makes them tick and what we can do to keep 'em happy on the trail.
Nature's Shock Absorbers
Despite being the hard, resistant structure it appears to be, your horse's foot is actually a resilient shock absorber of ingenious design: when the horse's foot hits the ground, here is the sequence of events that ensue:
1. The frog (the wedge-shaped mass on the bottom of the foot) takes the initial “hit”, dissipating much of the shock, while passing it up to --
2. The digital cushion, a mass of elastic fibers lying internally, above the frog. This cushion compresses, spreads out, and while absorbing much of what's left of the original shock, provides support and passes the now-diminished shock to --
3. The lateral cartilages. These cradle the coffin bone, suspended above the sole of the hoof; these cartilages, having absorbed most of what's left of the original shock, transfer the remains of the shock to the coffin bone. The coffin bone is the lowest member of the bony column that comprises the horse's leg, and the first component of her structural support system – her skeleton – which now distributes what's left of the original shock to her body's joints, tendons, and ligaments.
There is a huge bonus attached to this process, the extra “gift” mentioned above: during step 3, the sole of the hoof momentarily flattens, and the horse's heels spread, allowing still further dispersal of the shock, and in addition some blood from within the hoof itself is temporarily “pumped” out of the foot by the horse's weight suddenly being applied. But a moment later, that foot is up again, off the ground, and by thus removing the horse's weight, the hoof is expanding – drawing blood back into itself! Imagine that – it's actually functioning as a heart, pumping blood with each step! What's amazing about it is that demand from all working muscular movement burns oxygen, and this quasi-heart action in each hoof is augmenting major oxygen delivery throughout her system, normally provided by her heart alone, thus giving her heart an extremely valuable boost, and extending her endurance almost immeasureably!
And remember, there are four hooves, all built and working the same way, and there are millions of hoof shock dissipation events over the course of the horse's life span. There is a limit, however, to how much energy your horse's foot can safely deal with. The structures in the foot can absorb and transfer energy without injury only if the amount of energy entering the foot and the frequency of concussive impacts do not exceed certain limits. If you overload your horse's foot by galloping on hard ground, for example, you can overwhelm the shock absorbers, increasing the chances of foot injuries such as sole bruises, pedal osteitis (coffin bone inflammation), and arthritis.
The effectiveness of a horse's shock absorbers also varies according to the animal's conformation. Horses with small hooves relative to their body size are prone to concussion injuries because of the limited surface area available to absorb shock. Horses with straight joints like upright pasterns, or straight shoulder angles, or straight hocks are also predisposed to concussion injuries. Angled joints are better shock absorbers than straight joints because the tendons and ligaments stretch out around the angled joint and absorb more of the impact. In straight joints, concussion forces are transferred directly from bone to bone through just a layer of joint cartilage, without mitigation by elastic ligaments and tendons. Over time the bone and cartilage deteriorate, resulting in arthritis.
How you can help
You can help matters by protecting your horse's natural shock absorbers. For example, ride on soft surfaces as much as possible (but avoid overly soft surfaces, such as deep sand. Such surfaces tend to pull or tear at his tendons and ligaments because he's constantly struggling to maintain his balance on the soft surface).
Regular hoof care is important to help your horse avoid concussion injuries. Have your trimmer or farrier regularly trim or shoe your animal's hooves so that the hoof walls don't break or grow out of balance. Pay special attention to the edges of her hooves if your horse is not shod: normal wear and tear chips away hoof material as a matter of course, but some hooves are weaker than others, and in short order the weak ones can suffer some serious hoof wall chipping. Your barefoot trimmer should know how to trim such wear and tear on hooves; it's up to you to make sure he does it.
On the matter of metal shoes, soft aluminum shoes can absorb some concussion because they deform on impact and wear away a bit each time they hit the ground. On the other hand, hard-metal shoes can't dissipate as much concussion because they don't deform or wear as much. If you want to use a hard-metal shoe, ask your farrier to add a cushioning pad between the shoe and your horse's hoof. Further, if your farrier is not already using them, ask him to put a rubber rim pad on the shoe to absorb the shock. Rim pads are shoe-shaped strips inserted between the metal shoe and the hoof.