Kissing spine is a skeletal abnormality in horses in which bony growths on the vertebrae of the spine touch or “kiss”. These bony outgrowths are called dorsal spinous processes.

This condition is caused by multiple factors including conformation issues, genetic predispositions, poor posture, improper conditioning, and training under saddle at a very young age.

Horses with kissing spine do not always develop symptoms, but many horses with this condition experience back pain. Afflicted horses may exhibit extreme back tightness, bucking, pain on palpation and an inability to stretch and raise the back while under saddle.

Most horse owners dread having their horse diagnosed with kissing spine. For a long time, it was thought that horses with symptomatic kissing spine could no longer be ridden and had to be retired.

However, surgical advances and modern rehabilitation techniques give new hope to owners of horses with kissing spine. There are many therapies available to keep your horse comfortable and to re-establish mobility.

Have your veterinarian examine your horse if you think they are experiencing back pain. If left untreated, horses with kissing spine can act out under saddle, putting themselves and their riders at risk.

Kissing Spine: An Emerging Concern

Kissing spine is sometimes referred to as dorsal spinous process impingement syndrome.

Kissing spine commonly affects multiple vertebrae of the lumbar spine, the area of the spine distal to the ribs. However, it can occur along the entire length of a horse’s back. [2]

This condition is diagnosed by a veterinarian upon radiographic detection of overriding dorsal spinous processes (ORDSP). Kissing spine diagnosis has increased significantly in recent years due to the increased use of x-rays. [2]

Your veterinarian will perform x-rays along the spine to determine whether the vertebrae in the spine are too close or touching. When examining an x-ray of the back, veterinarians look for reductions in the space between dorsal spinous processes and changes to the boney areas.

Dorsal spinous process impingement syndrome in horses

Your vet may also suggest a bone scan (scintigraphy), which involves injecting your horse with a radioisotope.

A bone scan camera is positioned over your horse’s back to detect hot spots – areas where radiation is absorbed into the bone. These hot spots indicate areas of inflammation and likely pain. [1]

Back Pain in Horses

Kissing spine does not always cause pain. In fact, some cases of kissing spine are found accidentally while investigating other issues in asymptomatic horses.

However, when kissing spine does cause pain it can be quite severe. Horses with this condition can experience pain for the following reasons:

  • The bony dorsal spinous processes grinding against each other
  • Pinching of the ligaments between the processes
  • Reduction of range of motion and resulting muscle stiffness
  • Impingement of the nerves exiting the spinal cord

Causes of Kissing Spine

Although research is ongoing, scientists have determined that kissing spine is a result of multiple factors.

Predisposed Breeds

Research has indicated that Warmbloods, Thoroughbreds, and Quarter Horses are more likely to develop kissing spine than other breeds.

This may be a consequence of genetic factors as many horses of these breeds trace back to the same sires. It may also be because these breeds tend to be ridden at younger ages than other breeds. [2][3]

Conformation

Horses with shorter than average backs are more likely to develop kissing spine. These horses have the same number of vertebrae in a smaller area, resulting in decreased space between the vertebrae. [4]

Genetic Component

Researchers have identified a strong genetic link to kissing spine. Although the full study has not yet been published, Etalon Diagnostics indicates that horses born from parents with kissing spine are more likely to develop the condition later in life. [5]

Improper Conditioning

Horses that are ridden with a high head and hollow back or trained under saddle too young are more likely to develop kissing spine. [4]

If the horse’s topline and back are weak and unable to carry a rider properly, the dorsal spinous processes are not able to lift and spread.

This can continue until the bones rub together or fuse, resulting in extreme pain. [6]

Negative Plantar Angle

Negative plantar angle refers to a collapsing of the hind heels or tipping up of the coffin bone. The toe of the coffin bone is slightly higher than the heel, resulting in uneven pressure on the hoof wall and sole.

When the coffin bone rotates upward, the horse must move its hind limbs in a way that stiffens the back in a hollow posture. [7] Consistent movement in this posture will bring the dorsal spinous processes closer together, resulting in kissing spine. [8]

Accompanying Conditions

Horses with kissing spine often have hock and sacro-iliac arthritis [8]. When horses move incorrectly in their back, they will often move incorrectly in their hind end as well.

A horse with a diagnosed kissing spine should also have sacro-iliac and hock x-rays to determine if treatment for arthritis in these areas is warranted.

Signs & Symptoms

Although kissing spine is not always symptomatic, horses who do experience pain can display a wide variety of signs such as:

  • Bucking under saddle
  • Reluctance to stretch the neck and round the back
  • Hind end lameness
  • Discomfort when saddling or doing up the girth
  • Weight loss
  • Cross cantering or difficulty maintaining a canter
  • Pain when palpating or brushing the back
  • General irritability when moving

Because these symptoms are also associated with other conditions, it is important to discuss diagnosis with your veterinarian to rule out other health problems including:

Treatment

In the past, a diagnosis of kissing spine would be a career-ender for performance horses.

Fortunately, there have been significant improvements in surgical, pharmaceutical, and rehabilitative interventions that give hope to many kissing spine horse owners.

The prognosis for horses with this condition is much better today. The majority of horses with kissing spine can return to work after following a veterinarian-recommended treatment plan. [13]

Treatments in use today include surgery, joint injections and non-invasive rehabilitation.

Interspinous Ligament Desmotomy

Pioneered by Dr. Richard Coomer in 2009, the interspinous ligament desmotomy (ISLD) is colloquially referred to as the ligament snip.

This procedure aims to cut the ligament between the spinous processes of the affected vertebrae, removing the source of pain and re-establishing mobility. [9]

While your horse is under standing sedation, the surgeon will make small incisions above the areas of kissing spine. The surgeon uses a very small chisel to divide the interspinous ligament in half.

Following ISLD, your horse will be on stall rest and a rehabilitation protocol as direct by your veterinarian.

This surgery comes with minimal complications and a high long-term success rate (90%). However, it does have its limitations. [9] Horses with widespread areas or extremely close spinous processes are not good candidates for ISLD.

ISLD does not cure kissing spine, but it does minimize symptoms and allow the back to move comfortably during rehabilitation.

If not rehabbed properly, some horses experience recurrence of kissing spine or develop kissing spine in other areas.

Cranial Wedge Ostectomy

The standing wedge ostectomy (or bone shave) is a much more invasive procedure, but it removes the kissing spines completely.

This surgery can be performed with your horse standing or lying on its side. The surgeon will make a large incision down the length of your horses back over the areas affected by kissing spine.

The surgeon will then cut through the supraspinous ligament, which is the large band of fibrous tissue that runs along the top of the spinous processes.

Using a bone saw, the surgeon will then remove small sections of the overlapping spinal processes, curing the kissing spine. With the supraspinous ligament re-attached, your horse is now ready for stall rest and rehab. [10]

This surgery has an increased risk of infection and complications. After the surgery, remaining parts of the spinous processes can become sharp and irritated.

Without proper rehab protocols, kissing spine can recur in other areas of your horse’s back. [10]

Joint Injections

Similar to joint injections used to treat issues in the lower hock joints, injections between the spinous processes can temporarily improve comfort and mobility.

Your horse is sedated and a needle is inserted into the spaces between the kissing processes to administer corticosteroid medications.

These drugs have an anti-inflammatory effect that reduces pain and stiffness between the joints, allowing you to exercise your horse and help them build topline. [3]

Your horse may not be a good candidate for joint injections if the spinous processes are too close together or are fused. Joint injections are temporary; your horse may need repeated injections in order to remain pain-free.

Mesotherapy

Joint injections are often accompanied by mesotherapy and robaxin. When performing mesotherapy, a veterinarian uses very small needles in multiple locations to inject medication into the mesoderm – the deep layers of the skin.

The medication is a solution consisting of anesthetic carbocaine, corticosteroids Pred-Forte or Dexamethasone-SP, and sterile water. [11] This solution numbs the pain sensors in the back and will relieve some symptoms of kissing spine.

Robaxin (methocarbamol) is a muscle relaxant that is given to ease tension in your horse’s back muscles.

All of these treatments must be combined with conditioning to produce a positive long-term result. [12]

Non-Invasive Techniques

If your horse is not a candidate for the invasive therapies listed above, there are non-invasive treatments that can prove very successful.

Non-invasive approaches to rehabilitation involve:

  • Conditioning exercises that strengthening the abdominal muscles and topline
  • Anti-inflammatory medication such as Equioxx
  • Corrective farriery
  • Shockwave therapy
  • Chiropractic care
  • Diets that are low in sugar and starch to limit inflammation [14]

Any treatment plan for kissing spine must include conditioning to strengthen the topline and abdominal muscles. If your horse has a weak topline the spine will collapse on itself, bringing the spinous processes closer together.

Summary

If you suspect that your horse has back pain or kissing spine, consult with your veterinarian to obtain an accurate diagnosis.

Your veterinarian will tell you how advanced your horse’s kissing spine is and what treatment options are available. You may also want to consult with a rehabilitation specialist with experience treating horses with kissing spine about non-invasive therapies to support recovery.

You can also submit your horse’s diet online and our nutritionists can help you design a feeding plan to reduce inflammation and support the development of topline muscles.

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References

  1. Ericshen, C. et al. Relationship between scintigraphic and radiographic evaluations of spinous processes in the thoracolumbar spine in riding horses without clinical signs of back problems. Equine Vet J. 2010.
  2. Musu Mayaki, A. et al. Clinical investigation of back disorders in horses: A retrospective study (2002-2017). Vet World. 2019.
  3. Sinding, F. and Berg, L. Distances between thoracic spinous processes in Warmblood foals: A radiographic study. Equine Vet J. 2010.
  4. Jeffcott, L. Disorders of the thoracolumbar spine of the horse — a survey of 443 cases. Equine Vet J. 1980.
  5. Etalon Diagnostics. Identification of Genomic Loci Associated with Performance-Limiting Kissing Spines in Quarter Horses and Warmbloods. Am Assoc of Equine Prac. 2020.
  6. De Cocq, P. et al. Effects of girth, saddle and weight on movements of the horse. Equine Vet J. 2010.
  7. Clements, P. et al. An investigation into the association between plantar distal phalanx angle and hindlimb lameness in a UK population of horses. Equine Vet Edu. 2019.
  8. Bromiley, M. The foot and shoe as a possible cause of injury. Equine Injury, Therapy, and Rehab. 2007.
  9. Sayers, E. et al. An exploration of clinical reasoning and practices used by physiotherapists in the rehabilitation of horses following interspinous ligament desmotomy surgery. Physio Theory and Practice. 2020.
  10. Jacklin, B. et al. A new technique for subtotal (cranial wedge) ostectomy in the treatment of impinging/overriding spinous processes: Description of technique and outcome of 25 cases. Equine Vet J. 2013.
  11. de Faucompret, P. The mesotherapy treatment of the dorso-lumbar arthropathies of the trotting horse. Bulletin de l’Academie Veterinaire de France. 1985.
  12. Forney, B. Methocarbamol for Veterinary Use. Wedgewood Pharm. 2021.
  13. Prisk, A.J. and Garcia-Lopez, J.M. Long-term prognosis for return to athletic function after interspinous ligament desmotomy for treatment of impinging and overriding dorsal spinous processes in horses: 71 cases (2012–2017). Vet Surg. 2019.
  14. Suagee, J.K. et al. Effects of High-Sugar and High-Starch Diets on Postprandial Inflammatory Protein Concentrations in Horses. J Equine Vet Sci. 2015.