Swayback Horse – Understanding Equine Lordosis
- What is Swayback?
- Anatomy of the Equine Topline
- What Causes Horses to Develop a Swayback?
- Riding, Care, and Maintenance of a Swayback Horse
- Prevention of Swayback
- Evidence-Based References
Updated June 6, 2024 | By: Andris J. Kaneps, DVM, PhD, DACVS, DACVSR
What is Swayback?
Swayback, also referred to as equine lordosis, involves excessive downward curvature of a horse’s midback spine.
Normally, the thoracolumbar spine (the section between the horse’s withers and croup) is aligned to be almost parallel with the ground. With swayback horses, there is a noticeable curve of the back alignment directed toward the ground.
The opposite in conformation, called kyphosis or roach-back in horses, is a curve of the back directed up and away from the ground. A sideways or lateral curve of the spine is known as scoliosis.
Swayback in horses is very uncommon. In a survey of 443 horses with back issues, 2.9% had malformations of the vertebral column, including lordosis, kyphosis, and scoliosis [1].
Ask the Vet Video on Swayback in Horses
Watch as Dr. Lydia Gray explains the causes of swayback and the importance of having a properly fitted saddle if you’re riding a horse with this conformation.
DAN: "What causes swayback, and how do you prevent it?"
DR LYDIA GRAY: Well, there's no answer to either of those questions. So we're done.
DAN: That's the end of the episode.
DR LYDIA GRAY: So sway back would be the colloquial term, and the term that the veterinarian would use is lordosis. And lordosis means an inward curve of the spine or an arch, versus a kyphosis is an outward curve or a hunch, and then scoliosis is a sideways or lateral curve. They all have names. It's hard to tell what she's thinking of. There's early onset lordosis, like in a young horse, and then there's the old-age associated or late-term.
DAN: Which most people feel is common to see.
DR LYDIA GRAY: As the horse ages, the soft tissues that hold the spine rigid begins to sink. Those tissues become lax or loose, and the muscles in the belly and the back sort of become less strong, and the whole thing sort of sags over time.
DAN: OK, so the muscles in the abdomen is not strong enough to also keep the back up, plus the back muscles are--
DR LYDIA GRAY: Ligaments and the tendons, they're sort of loosening, and softening, and not doing-- they're not as structurally sound. But it's different in the young horse. There's a theory that the young horse-- there's a deformity in the vertebrae themselves. Because if you're 18 months or two years old, and you have not a gentle sag like an older horse, but a pretty extreme-- that looks different, and you would suspect the bony shapes to be different, and radiographically, it's been shown they are.
DAN: So there's something more severe going on.
DR LYDIA GRAY: Yes, but interestingly enough, horses are one of the only species that can have a significant lordosis and not be affected. They can still have a normal, long, healthy, productive life.
DAN: But could you ride them?
DR LYDIA GRAY: Yes.
DAN: Interesting.
DR LYDIA GRAY: Yeah. It does not seem to affect their performance, their way of going, they could still be a brood mare.
DAN: We've all seen that horse who looks a little dipped in the back, where it's a nice little seat for you to sit in, but I always thought there might be some discomfort that goes along with that.
DR LYDIA GRAY: It doesn't appear to be, just talking about the back issue. Now, when you put a saddle on, then you could create an issue because if you've got a back that dips, now you've got the potential to create bridging, where the front of the saddle and the back of the saddle touch, but the middle doesn't.
DAN: OK, so now you're hitting weird pressure points.
DR LYDIA GRAY: Yeah. So now you have to be really, really careful that your saddle fits if you're going to have-- if you're going to continue to ride it. A horse that ages into it or a horse that just has it from the get go.
DAN: Well, there are a lot of saddle pads now that are designed to kind of help with some of that bridging for horses who do have some sway back to kind of help that out a little bit.
DR LYDIA GRAY: Yeah, and I would probably engage in services of a saddle fitter to make sure. A couple more things I wanted to say was that the reason this is not studied a lot-- and so causes and prevention and correcting-- is because only about 1% the general horse population has this, and it's just not enough for the money to be there to research it. About 7%, though, of American Saddlebreds have this.
DAN: I was going to say.
DR LYDIA GRAY: I'm sure you were thinking that. It can happen to any horse, but Saddlebreds, they are now confidently saying there is a heritable or genetic component to it. The specific gene has not been identified, but they're really close. They do know that the gene is recessive, not dominant, which means you have to have two copies of it to show it. So the sire and the dam must both have a copy, if you remember your Mendelian genetics.
DAN: I remember my little Punnet square. I knew it would come in handy one day.
DR LYDIA GRAY: So it's seen more often in Saddlebreds, and when it comes to the causes-- for Saddlebreds, at least-- there is a genetic component. Preventing it, other than not breeding two horses that have it, that's the only way you can prevent it. And then once it begins, there's not really anything you can do about it.
DAN: Well, I was just going to say there's not any sort of exercises you could do to help support the abs and make sure the horse is engaging?
DR LYDIA GRAY: Maybe for the old age onset version of it, you could encourage them to have that lift in the back, and the roundness, and you do exercise that support-- the abdominal muscles, but I think you're just prolonging it or extending their normal lifespan. Or slowing the progression down.
DAN: It's not going to cure it.
DR LYDIA GRAY: You're just slowing things down. Slowing the inevitable down.
Anatomy of the Equine Topline
The horse’s spine is like a bridge. With its associated muscles and ligaments, the spine must carry the weight of the entire abdomen, plus a rider!
Muscle Groups
A horse can develop swayback due to loss of muscle tone in the topline muscles, such as the longissimus dorsi, multifidi, and iliocostalis.
The iliopsoas muscle group connects the spine to the pelvis and femur. It provides stability to the caudal spine, and when activated, will cause the back to arch (kyphosis).
The abdominal muscles play an important role in carrying the weight of the belly contents and stabilizing the back (internal abdominal oblique, external abdominal oblique, transversus abdominus, and rectus femoris muscles).
Stabilizing Ligaments
Ligaments also help stabilize the spine and can be injured or stretched, which may cause the spine to drop. Stabilizing ligaments of the back include:
- Supraspinous: located along the top of the dorsal spines of the vertebrae;
- Interspinous: between the dorsal spines;
- Ventral longitudinal ligament: lies on the deep surface of the vertebrae.
These ligaments reduce the amount of extension or flexion of the spinal column of the back.
What Causes Horses to Develop a Swayback?
The most common causes of swayback in horses include:
- Loss of muscle tone (topline and abdominal muscles)
- Stretching or injury of the ligaments that stabilize the spine
- Genetic basis (more commonly occurs in American Saddlebred horses)
- Injury or birth defects of the vertebrae of the back
Loss of muscle tone alone can cause varying degrees of swayback, even in sound, active horses. Muscle tone loss can happen with injuries or when a horse is somewhat inactive, like when they are retired. It most commonly occurs in older horses and broodmares that have carried multiple pregnancies.
Back injuries, such as malformations early in life or a fracture, may also cause swayback. Spinal conformation abnormalities can occur due to malposition of the developing fetus prior to birth or injury during the birthing process.
Inheriting Swayback
Swayback found in American Saddlebred horses may be caused by a recessive gene that can be passed to offspring. In a group of 305 Saddlebred horses that had their back conformation measured, 7% were determined to have swayback [2].
Saddlebreds with heritable swayback (having the genetic component) may manifest conformational changes at as early as 18 months of age. The location of the genes that may cause heritable swayback has been identified [3].
Swayback associated with heritable birth defects has also been identified in Haflinger horses [4]. Three foals sired by the same stallion were born with swayback and evaluated to have similar deformities of several vertebrae.
Riding, Care, and Maintenance of a Swayback Horse
Most horses with mild swayback do not experience pain or discomfort and may have normal athletic careers. Your veterinarian can help assess a safe level and amount of exercise and riding for your swayback horse.
Your vet will examine your horse and possibly take radiographs (X-rays) of the back. They will identify any discomfort on palpation of the back, and X-rays will identify any abnormalities of the vertebrae.
If your vet determines your swayback horse is comfortable for riding, then special care should be taken to provide appropriately fitted saddle and saddle pads that will properly distribute the weight of the equipment and rider over your horse’s back.
Core Strengthening Exercises
Any horse, but especially a horse with swayback conformation, should undergo regular core strengthening exercises [5].
Exercises you can do from the ground that strengthen the topline and abdominal muscles involve a variety of carrot stretches – core strengthening exercises you can do with any treat your horse prefers. You can do these on the ground for about 15-20 minutes and repeat 3-5 times per week. Carrot stretch exercises include rounding, lateral bending, and neck extension stretches [6].
Core muscles may also be strengthened during training with proper collection and using Equiband® equipment that may be used under saddle or on the lunge line. Exercises over ground poles and cavalettis can also help your horse build core strength and flexibility.
Prevention of Swayback
There is no secret to preventing swayback other than maintaining your horse’s fitness and core strength. Even if your horse cannot be ridden due to weather, illness, or injury, the stretching exercises will help maintain core strength and give your horse a job to focus on. Besides maintaining core strength and flexibility, the reward of a carrot or two is appreciated by all horses!
Evidence-Based References
- Jeffcott, L. B. “Disorders of the Thoracolumbar Spine of the Horse — a Survey of 443 Cases.” Equine Veterinary Journal, vol. 12, no. 4, Oct. 1980, pp. 197–210. https://doi.org/10.1111/j.2042-3306.1980.tb03427.x.
- Gallagher, Patrick, et al. “Measurement of Back Curvature in American Saddlebred Horses: Structural and Genetic Basis for Early-onset Lordosis.” Journal of Equine Veterinary Science, vol. 23, no. 2, Feb. 2003, pp. 71–76. https://doi.org/10.1053/jevs.2003.21.
- Cook, Deborah, et al. “Genetics of Swayback in American Saddlebred Horses.” Animal Genetics, vol. 41, no. s2, Nov. 2010, pp. 64–71. https://doi.org/10.1111/j.1365-2052.2010.02108.x.
- Coates, John W., and Ronald C. McFee. “Congenital Lordosis in Three Haflinger Foals.” PubMed, vol. 34, no. 8, Aug. 1993, pp. 496–98.
- Clayton, Hilary M. “Core Training and Rehabilitation in Horses.” Veterinary Clinics of North America: Equine Practice, vol. 32, no. 1, Apr. 2016, pp. 49–71. https://doi.org/10.1016/j.cveq.2015.12.009.
- Stubbs, Narelle C., and Hilary Mary Clayton. Activate Your Horse’s Core: Unmounted Exercises for Dynamic Mobility, Strength, and Balance. 2008.