It’s the equine body part that might seem most essential to the rider. It’s where we put all our weight, where we place our favorite (and most expensive) riding gear, where we connect—directly, physically—with our mount, and where we communicate with subtle cues.
But for all its importance, equine researchers say the equine back remains largely misunderstood by many riders. How is it built? How does it work? How much weight can it hold? How do we know its health is compromised, and what are the consequences? And, perhaps most importantly, what can we do to prevent back problems, and what treatments do we pursue if they do get injured?
Back to Basics
What horse people often refer to as the “back” is simply the dipped area of the spine between the withers and the croup. But a true consideration of the equine back requires looking at its entire length, from the withers to the top of the tail, says Hilary Clayton, BVMS, PhD, MRCVS, Dipl. ACVSMR, McPhail Dressage Chair Emerita at Michigan State University and president of Sport Horse Science, in Mason, Michigan. That’s because the full spine is involved in the horse’s back movement, all the way down to the sacrum (the “downhill” croup section from the high point behind the saddle area down to the tail).
Most horses have 18 thoracic vertebrae—the bones we’re essentially sitting on when we’re riding. They’re also the bones from which the ribs flare. Five vertebrae make up the sacrum area, and these are usually fused together. Between these two spinal sections is the lumbar area, with numbers of vertebrae varying from one horse to another.
“Typically, horses have six lumbar vertebrae, but about a third of them only have five (with the sixth one joined to the front part of the sacrum and considered a part of that structure),” Clayton says. “It’s the most variable part of the horse’s spine.” Sometimes the first lumbar vertebra will even have a small rib coming out of one or both sides.
Lumbar vertebrae number doesn’t seem to affect back length, however. It appears that it’s the length of individual vertebrae, and not the number of them, that makes horses longer- or shorter-backed, Clayton says. And the number of vertebrae seems to have no bearing on the horse’s physical appearance or spinal health.
The canal that houses the spinal cord is nestled about five inches beneath the horse’s topline, which is formed by the bony spinous processes sticking up from each vertebra. A layer of short muscles, called the deep stabilizing muscles, lies very close to the vertebrae, crossing one to four intervertebral joints. These muscles do what their name suggests, keeping the spine from becoming “rubbery and bending when the hind limbs provide propulsion and (preventing) the type of micro-motion that predisposes the joints to the development of arthritis,” Clayton says.
Long muscles lie atop the vertebrae, and these are the ones we sit on and can palpate, she says, and are the muscles of athletic movement.
In addition to this long and short muscle series is a whole network of long and short ligaments. “The long ones go along the underside of the vertebral bodies and then along the topline just under the skin, so there’s actually the long supraspinous ligament holding everything together from around the fourth thoracic (the fourth or fifth vertebra in this section, T4/5) all the way to the last lumbar,” Clayton says. That big ligament acts like a taut rubber band, preventing the spinous processes from getting pulled too far apart.
“Everything is very firmly held together,” she says. “It’s pretty amazing that you can take 20-something little bones and attach them together with ligaments and muscles so they can actually support the weight of a rider.”
Strengthening and Conditioning
We’re often told that our horses need “gymnastics” to become supple and flexible, and that they should be able to curve their bodies around our legs or when working in circles. But those gymnastic exercises are mostly for getting the rest of the body—mainly the limbs—in full movement, and not the back.
“We want to maintain a full range of motion in the back when the horse is standing, but the goal is not to maximize back flexion and extension when the horse is in motion,” says Clayton. “During locomotion the main function of the muscles, tendons, and ligaments is to control the amount of back movement. Our training goal is to strengthen the muscles that will stabilize the back in a rounded position.”
What Clayton is talking about is the concept of rounding—getting horses to raise their backs under saddle to offset the effect of the rider’s weight. While horses are physically capable of supporting a rider, any added weight on that back can cause hollowing—or swaying. “Rounding the back counteracts the hollowing effect, limiting the amount of sinking,” she says.
But getting a horse to round his back requires focused effort toward building strength in both the back and the abdominal muscles over time. Horses must also have good strength of these structures to bend to the left or right when working in circles, Clayton adds. So asking them to work small circles or bend around a rider’s leg before they’re ready can lead to back problems and possibly behavior problems related to discomfort and frustration, as well. “An untrained horse just can’t bend his body around a 10-meter (30-foot) circle,” she says.
With young horses, focus on strengthening the short stabilizing muscles and the abdominal muscles. The abdominal muscles are actually responsible for supporting the rider’s weight and for rounding, so they’re critical, says Katja Geser-von Peinen, DVM, clinical researcher in the Department of Sports Medicine at the Equine Clinic of Vetsuisse Faculty, in Zurich, Switzerland.
While the back itself needs to stay fairly immobile, the back muscles need to be working and moving constantly to keep the back stable during movement. “The long back muscles are actually responsible for controlling the sideways movement of the spine,” she says.
Not respecting the muscles’ purpose can lead to back pain and hollowing, says Geser-von Peinen. So riders need to learn to ride correctly, which means finding a good coach with a history of training healthy-backed horses, who can instruct you from the ground, prompting you to ride for roundness. And remember that a round head and neck position does not mean your horse is going round. “Some horses have nicely curved necks but still have hollow backs,” she says.
Riders also need to respect a gradual increase in mounted work time—progressing slowly as the horse’s back and abdomen build muscle mass, she adds.
The Importance of the Saddle
Correct saddle fit is essential to back health. But because horses’ back shape and musculature change over time, proper saddle fit can be both a perennial challenge and a huge expense. Clayton says recent research out of the Animal Health Trust in Newmarket, U.K., shows that back shape changes several times over the course of just a year.
Saddle pads aren’t really meant for fixing poor saddle fit. But buying a new saddle every time the horse’s back changes isn’t realistic either!
Learn how to recognize when a saddle fits and doesn’t fit and know when it’s necessary to call in a professional to reflock the saddle to conform to the horse’s evolving back shape, Clayton says. Lumps, bumps, bruises, and lesions are obvious signs of a saddle fit problem, as is a negative reaction to the saddle in general.
Believe it or not, one of the best ways to keep your horse’s back healthy is to keep your own back—and rest of your body—healthy. Geser-von Peinen says rider asymmetry is a major source of equine back problems. “Make sure you’re as symmetric as possible” in the saddle, she says. That means also keeping up a good fitness program for yourself so that you sit and move correctly.
“When you’re fit you’re able to sit gently, because you have the muscles to stabilize your body for a whole lesson,” explains Geser-von Peinen.
Keeping yourself trim also helps safeguard your horse’s back. When you add your tack, equipment, and clothing, the total weight you’re putting on a horse is not negligible. And when you consider how that weight multiplies during movement, you’re dealing with some significant pressure! Clayton says maximum forces on a horse’s back are about double the rider’s weight at the trot, and they’re up to three times that weight at the canter. “The rider’s weight really does matter!” she says.
The Warning Signs
Most horses with back pain are active or retired riding horses, says Geser-von Peinen. So we really need to keep a close eye on how our mounts’ backs are holding up to their workouts.
First, she says, get in the habit of evaluating your horse’s back shape. Every time you groom him, look for changes such as muscle loss in the back. A horse in training should be building muscle, not losing it. If you see dips behind the shoulder blade or a triangular shape instead of a rounded shape over the thoracic, lumbar, or sacral areas, take caution: your horse is a candidate for back pain.
Second, observe his attitude. Does he turn his tail to you when you show up with a saddle? Is he depressed or moody? Does he flinch or threaten to bite when you girth him up? Is he sensitive when you press on his back muscles? Does he buck under saddle? Does he lean on the reins? Do you have to warm him up for 30 minutes to get him supple? And mostly, is this a trend? “It’s okay to have a bad day, but if it goes on for a week or more, especially if it’s getting worse, contact your veterinarian,” says Geser-von Peinen.
And finally, keep an eye on your Thoroughbreds and Thoroughbred crosses. “Thoroughbreds are more sensitive to pressure, although we don’t really know why except that they have thinner skin and a touchier personality,” Geser-von Peinen says. “The important thing is that we have to be careful about their backs.”
It’s worth having your veterinarian examine your horse’s back annually, she says. And if you use a veterinary chiropractor, don’t rely on adjustments alone. Be sure to have your veterinarian investigate recurrent issues; otherwise, you might only be temporarily managing the signs instead of the underlying problem.
To Treat or Not to Treat
If you can catch the warning signs of back pain early enough, try changing your training program to build the deep stabilizing muscles and to encourage the horse to round his back. If the problem isn’t showing rapid (within a week) improvement, call your veterinarian. “It’s easy and inexpensive to treat with oral anti-inflammatory drugs,” says Geser-von Peinen.
If you wait, you can create what she calls “a vicious cycle.” If the back muscles hurt, the horse stops using them. If he stops using them, they get depleted, and this just makes the pain worse.
This can lead to “micro-movements”—a sort of vibration—in the facet joints between the vertebrae, which are common sites for arthritis in athletic horses. Treatment of facet arthritis can require ultrasound-guided anti-inflammatory injections and a several-month-long rehabilitation program. Better, then, to avoid downtime by being proactive in preserving your horse’s back health.
The equine back is an intricately designed structure, capable of supporting the horse’s body mass and shape—as well as a rider. But to keep that back healthy and pain-free, we need to be conscious of the structures at play and, more importantly, how to build muscles in the area to keep it strong. By implementing proper training and riding techniques, making our own fitness a priority, and recognizing early signs of pain and pursuing treatment, we can be sure our horses’ backs remain the powerhouses they were designed to be.