Swayback Horse – Understanding Equine Lordosis
Updated April 19, 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.
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.