Kissing Spine (KSS), is the overriding or impinging of the dorsal spinous processes (DSPs). This means that either two or more vertebrae (DSPs) are touching or overlapping (Turner 2011). There are five different areas of the horse’s spine, including the cervical vertebrae, the thoracic vertebrae, the lumbar vertebrae, the sacral vertebrae, and the coccygeal vertebrae. Normal interspinous space between the DSPs of each vertebrae is 4mm wide (Sinding and Berg 2010). Therefore, when spacing is less than 4mm wide, this could put the horse at a higher likelihood of developing KSS.
A radiograph of a horse’s spine, showing the areas of the spine where KSS occurs. Each arrow points to an occurrence (Turner 2012).
The grading scale for KSS is a 0-7 scale, which gradually increases based on the severity and stage of KSS. 0 is considered to be normal spacing between the DSPs, followed by grades for mild narrowing of the spacing, more severe narrowing of the spacing, impinging of the DSPs, more severe impinging of the DSPs, fusing of the DSPs, and lastly, severe abnormalities and bony bridges between the DSPs in addition to fusing, which would be considered a 7 (Zimmerman et al. 2011). Considering all grades and severity of KSS, the syndrome occurs in 39% of horses (Turner 2011). And while it can occur in horses of all ages, disciplines, and breeds, Thoroughbreds have the highest instances of KSS and the narrowest interspinous spaces out of all breeds (Jeffcott 2005).
The diagram on the left shows what normal DSPs of the equine spine should look like, with no impinging or overriding. The diagram on the right displays a horse with KSS, showing DSPs with severe overriding (Jeffcott 1980).
For horses of any breed, however, hydrotherapy could be a good means of helping a horse through the rehabilitation process when it comes to KSS. Combined with medical treatments that reduce pain, exercises that stretch and strengthen the back have been seen to be effective in increasing the longevity of the career of a horse with KSS, as this combination allows the horse to keep working (Turner 2011). Additionally, it is hypothesized that if antagonist muscles, like the abdominals, are not effective at flexing the spine, this could cause an increased risk for DSP overriding (Tabor and Williams 2018). Conversely, it could then make sense that exercises that increases the activity of the abdominals will increase flexion in the spine and potentially decrease the risk of DSP overriding. And after surgery—if that route is taken as primary action—one of the key aspects of rehabilitation afterward, according to veterinary surgeon Colin Mitchell, is increasing range of motion (2015).
Water treadmills, which are a form of hydrotherapy, could help in achieving these results. Water treadmills allow for a variation in water depth, and as the water depth increases, so does the horse’s range of motion. And the fact that it allows for variation in water depth means that it can target certain areas of the spine. An example of this is that increasing water depth causes an increase in extension in the cranial thoracic spine, and also increased flexion in the caudal lumbar spine. The water level can go up to abdominal height as well, which has been seen to cause flexion of the caudal thoracolumbar spine (Tranquille et al. 2017). With this information, the water level of the water treadmill could be adjusted to target the areas of the spine where the horse is affected by KSS. Additionally, a case study of a horse with KSS stated that after surgery and stall rest, the vet recommended using the water treadmill for rehabilitation (Scarsdale Vets 2017). With the benefits that come with using the water treadmill, it seems as though this form of hydrotherapy could be a good means of helping a horse with KSS.
By: Equine Kinetics, Inc., Pipersville, Bucks County, PA
Edited: Kristina Griffiths, MSc & Stefanie Simoni, BS
“CASE STUDY: Kissing Spines .” Scarsdale Vets, 4 Apr. 2017, www.scarsdalevets.com/kissing-spine-case-study/.
Jeffcott, L. B. (1980). Disorders of the thoracolumbar spine of the horse- A survey of 443 cases. Equine Veterinary Journal.
Jeffcott, L. B. (2005). Radiographic Features of the Normal Equine Thoracolumbar Spine. Veterinary Radiology & Ultrasound.
Mitchell, Colin. “Kissing Spines in Horses.” Equine Matters, 2015, pp. 9-10, www.xlvets.co.uk/sites/default/files/newsletter-files/Equine_text.pdf.
Sinding, M. F., & Berg, L. C. (2010). Distances between thoracic spinous processes in Warmblood foals: A radiographic study. Equine Veterinary Journal, 42.
Tabor, G. & Williams, J. (2018). Equine Rehabilitation: A Review of Trunk and Hind Limb Muscle Activity and Exercise Selection. Journal of Equine Veterinary Science, 60.
Tranquille, Carolyne A., et al. “Current Knowledge of Equine Water Treadmill Exercise: What Can We Learn From Human and Canine Studies?” Journal of Equine Veterinary Science, vol. 50, Mar. 2017, pp. 76-83, www.j-evs.com/article/S0737-0806(16)30370-7/fulltext.
Turner, T. A. (2011). Overriding Spinous Processes (“Kissing Spines”) in Horses: Diagnosis, Treatment, and Outcome in 212 Cases. AAEP Proceedings, 57.
Zimmerman, M., Dyson, S., & Murray, R. (2011). Comparison of Radiographic and Scintigraphic Findings of the Spinous Processes in the Equine Thoracolumbar Region. Veterinary Radiology and Ultrasound, 52.