What exactly is breakover? Most would answer that it is the horse's heel lifting off the ground and rotating over the toe as his foot leaves the ground. Breakover is simple in its definition, but pretty complex in its implications for your horse's movement and soundness. And there's not a lot of research out there yet to clearly define the best breakover for any horse.
In the meantime, while we wait for researchers to clarify the complicated interactions between hoof angle, hoof length, breakover point, shoe type, and the forces on the numerous joints and soft tissues in a horse's legs, we can look at what is currently known about breakover and how it can be managed to maximize your horse's soundness and performance.
Let's begin with the idea that breakover, however short, is a process rather than just an instant in time. World-renowned biomechanics researcher Hilary Clayton, BVMS, PhD, McPhail Endowed Dressage Chair in Equine Sports Medicine at Michigan State University, offered this definition of breakover in the Proceedings of the 2003 Bluegrass Laminitis Symposium:
"Breakover begins when the heels leave the ground and start to rotate around the toe of the hoof, which is still in contact with the ground. Breakover is initiated by tension in the deep digital flexor muscle and the distal check ligament (DCL, also known as the inferior or subcarpal check ligament), both of which act through the deep digital flexor tendon (DDFT), combined with tension in the navicular ligaments.
"On a hard surface, the hoof remains flat on the ground until heel off (the heel leaving the ground). On a softer surface, the toe rotates into the surface prior to heel off, which reduces tension in the DCL-DDFT and navicular ligaments. This, in turn, reduces pressure in the navicular region. Therefore, a surface that allows the toe to dig in during push-off is usually beneficial in horses with navicular syndrome or other types of caudal heel pain (see footing images here). Toe off is the instant at which the toe leaves the ground.
"The initiation of breakover is an important part of the stride, especially in horses with caudal heel pain. It's way more complicated than it looks at first sight."
One of the complications is that breakover to the front of the toe isn't the only issue; there's also breaking over to the sides to some degree, whether this occurs because a horse is turning or because his limbs are crooked.
Aside from what you see on the outside, there's also internal breakover to consider. Internal breakover is the movement and stress on the internal structures of the foot and leg that occur just before and during external breakover. Internal breakover is important because the stresses on these structures are directly affected by the mechanics applied to the outside of the hoof (i.e., trimming and shoeing). These structures must be managed properly in order to maximize a horse's soundness and to keep him sound longer.
"Imagine a horse standing still," says Ric Redden, DVM, founder of the International Equine Podiatry Center in Versailles, Ky. "As he starts to walk away, the first thing that tightens is the (deep digital flexor) muscle, which pulls (the deep digital flexor) tendon (DDFT), which in turn puts gentle pressure on the navicular bursa (the fluid-filled sac that cushions the navicular bone against pressure from the DDFT). Then that pressure acts on the navicular bone, then the impar ligament (which connects the navicular bone to the coffin bone, P3). The navicular bone also articulates with (adjoins) P2 (the short pastern bone) and is attached by the navicular suspensory ligaments. All of these structures become part of the process of breakover as tension is increased at the insertion of the tendon, which pulls on P3.
"As this bone begins to snug itself against the laminae, it pulls on the internal hoof wall, then the wings of P3 begin to lift. As they lift, the apex of P3 tips forward and begins the point of rotation. All this starts to happen before you can see even the most minute movement of the hoof capsule--this is occurring microseconds before the heel begins to lift.
"As the load is transferred throughout the foot, forces play out through different zones. The healthy foot will have equilibrium throughout each member as forces are passed from one stable member to another. If one member is diseased, traumatized, or less than healthy in any fashion, the adjoining member follows suit very quickly from the added stress of the failing member's job. This starts a cascade of events that deteriorates the entire equilibrium."
Now that we have an idea of what breakover entails, we might wonder about terms we've heard such as the angle of breakover or breakover point. We might also wonder about the value of manipulating breakover to improve a horse's gait or treat a problem, but we'll get to those in a bit.
The point of breakover is the most forward point of weight bearing when the horse is standing with his foot flat on the ground, says Chris Gregory, Fellow of the Worshipful Company of Farriers (FWCF), Certified Journeyman Farrier (CJF), owner of the Heartland Horseshoeing School in Lamar, Mo. If the ground surface of his foot is completely flat, then the point of breakover is the forward edge of his toe. If the ground surface is curved at all, whether his bare foot is worn that way or he's wearing a beveled, rolled toe, or rockered-toe shoe, then it will be farther back, somewhere in the belly of that curve (see diagrams). This point is often moved forward or backward in an effort to improve a horse's gait or make him more comfortable.
Another important point to consider is the shape of front vs. hind feet, Gregory adds. "The front foot has a round shape from widest point around the front to the widest point," he explains. "The hind foot has a sharper toe with a smaller radius. The front foot's rounded shape allows steering by allowing breakover at any point. The hinds are the driving force, and so the foot is pointier. The breakover in the front end needs to allow that steerability."
The ideal breakover parameters for any one foot will vary with that horse's way of going, leg conformation, and any pathology present. Breakover doesn't stand alone; it is impossible to separate it from hoof shape, balance, and length when it comes to manipulating the foot for treatment or performance. Ideally, all of these foot characteristics will be managed to distribute stresses on the various hoof and leg structures so that no structure is stressed beyond its intended capacity.
The most common manipulation of breakover is moving the breakover point back from the toe in an attempt to reduce the force required for the foot to move over the point of the toe, particularly in horses with heel pain or flexor tendon problems. Doug Butler, PhD, FWCF, CJF, author of 30 horseshoeing texts and tapes including Principles of Horseshoeing I and II, lists three reasons to change a horse's breakover: "To change action (also called motion or animation) for a show horse like a Saddlebred, to change the timing of the gait to influence gait defects, or to take off stress for a horse with disease by reducing the leverage required to break over."
For example, "For a navicular horse, you might use an egg bar, which helps keep the heels from sinking into the ground as much and thus keeps the angle higher, which relieves the stress on the flexor tendon and thus the navicular bone."
But how does one know when to manipulate breakover? Look at the wear of the shoe (or hoof if the horse is barefoot), says Butler. "The horse will tell you where his breakover should be. When I pull shoes, wear is the first thing I check, looking for an area that is worn more than the rest of the shoe."
"You can watch the horse move, but unless you have slow-motion video capability, you won't see much," he continues. "I visualize the horse's movement by the wear of the shoe. If he's putting more weight on the forehand, the fronts will be worn more (navicular horses are good examples of this). If there's more wear in the hind shoes, it's a horse that works with a lot of collection, like a dressage horse. You'll also see if the horse is putting more weight on one side of his foot than another by the wear."
Butler adds, "It will take about three shoeings to get (the solution) right. First you'll do what you think the horse needs, then the second time you read the wear on the shoe and modify your work according to that wear. The third time is checking up on the second visit's work."
Handle With Care
Like so many aspects of the horse's foot and the farriery trade, there really isn't a lot of research that can tell us exactly where breakover should be on a horse. There are, however, lots of cautions. Part of the reason for caution is that breakover isn't really one aspect of movement. "Manipulating breakover should be approached with care; there's so much we still don't know," says Clayton. "There are lots of factors to take into account, having to do with the various forces and kinematics (motions). If you only look at one of those, it's easy to come to the wrong conclusion."
For example, many horse people think that raising a horse's heels speeds his breakover by bringing him closer to breaking over when standing still. Raising the heels is thus a pretty standard practice when we want to encourage a horse to break over more quickly, for example, raising the heels on the front feet of a horse which strikes the bottom of his front feet with his hind toes (forging). However, while this practice might help stop a horse from forging, it's not by accelerating his breakover.
One of Clayton's studies found that adding a six-degree wedge pad to raise the heels actually delayed breakover and reduced the forces required to initiate breakover. This is likely because raising the heels decreases the stress on the DCL and DDFT that initiate breakover. Again, there are several components in the complex equine lower limb that have to be considered.
The key is to look at the conformation of the animal and not just his feet, says Butler. "We have to recognize what's there and apply a standard to that--lining up the phalanges (long and short pastern bones) parallel to the front face of P3 (the coffin bone)," he says. "That's the standard and has been the standard for 150 years, through the work of Dollar, Russell, Balch, the army horseshoeing manual, my books, and more.
"You can tell if your horse has these bones lined up pretty accurately by looking at the front of the pastern from the side with the horse standing on flat ground," he suggests. "Look at the line it makes with the upper third of the hoof and see if that line is straight. The lower two-thirds of the foot can be flared, dished, rasped back, etc., so just look at the upper third. If that line is straight, he'll be right most of the time. (If the lower two-thirds of the foot doesn't match the upper third, there is likely an imbalance resulting in uneven stress and a distorted foot.)
Redden notes that a farrier can usually make a problem foot look normal with a rasp, but then, "You've got the same foot, only less of it. I think it's essential to use radiographs to see what's going on inside the foot and not just look at the outside. Veterinarians and farrier podiatrists have to develop a very disciplined radiographic protocol to have one common way about speaking of soft tissue parameters in order to discuss internal balance as well as external balance."
"You need to use proper judgment with (breakover adjustment) and all other hoof manipulations," Butler says. "You have to ask, what are the mechanics of the foot and how can you improve them? You can't just try different things at random until you find something that works."
Another thing to remember with manipulating a horse's breakover--or anything else about his feet--is that if there is a problem, there might not be an immediate solution. In other words, you might not be able to go from a bad foot to a good foot in the time it takes your farrier to trim and shoe your horse. The real solution might be a gradual reshaping of a foot that has been compromised by poor balance or shoeing in the past. And this more gradual process might use different types or fits of shoes along the way.
So what can you do to improve your horse's breakover?
- Keep your horse on a good shoeing/trimming schedule so his feet don't grow too "out of whack" between farrier visits. The foot can grow up to three-eighths of an inch per month, which can change angles and balance quite a bit.
- If your horse isn't already trained to cooperate for hoof care, make him so. No one can fine-tune a moving target.
- Be there for your farrier's visits so you can talk to him/her about how your horse is moving and what work is being done. This way you can learn about the work and cooperate with him/her to design your horse's trimming/shoeing prescription.
- Don't talk to your farrier too much during the shoeing--he or she needs to concentrate on the job at hand, says Butler. "I really enjoy talking to the owner, but I do it before and after shoeing," he notes.
- If you are buying a horse, select him for conformation fitting the job he'll do, don't just look at how friendly his eye is or fall for the horse which licked your hand. "If someone paid $60,000 for a horse, you expect him to be perfect, but often these days we're seeing a lot of issues that will eventually defeat the veterinarian and farrier despite their best efforts," says Butler.
- Don't fall for the lure of the latest fix-everything fad that comes along without objectively evaluating it with your farrier. "When a horse wins a show or race, everyone wants to use what that horse is using without thinking if it's really right for their horse," Butler states. "We can't be so quick to follow the latest fad without thinking about it. They work for some horses, sure--even a blind squirrel finds a nut once in a while. But that doesn't mean it's right for every horse."
Every horse is special and different, and so are his feet. Finding his ideal foot shape and breakover point isn't easy, and it might take a little trial and error with an experienced farrier to find the foot conformation and shoeing strategy that helps each horse do his individual job well without overstressing any parts of the complex foot/lower limb.
About the Author
Christy West has a BS in Equine Science from the University of Kentucky, and an MS in Agricultural Journalism from the University of Wisconsin-Madison.
POLL: University Equine Hospitals