Is Kissing Spines in Horses Hereditary?

Kissing spines can have a genetic component, but it is not a simple “one gene equals disease” condition.

By Dr Duncan Houston

Kissing spines is one of the most frustrating back conditions in horses because it can sit in the grey zone between X-ray finding, performance issue, pain problem, training challenge, saddle-fit problem, and possible inherited risk.

Some horses have radiographic kissing spines and show no obvious signs. Others become painful, resistant, difficult under saddle, or unable to perform comfortably. That is why the real question is not just “does my horse have kissing spines?” It is: is this actually causing pain, why did it develop, and should this horse be bred, trained, treated, rested, or rehabilitated differently?

The hereditary question is important, especially for breeders and owners of Thoroughbreds, Warmbloods, and stock-type horses. Current research suggests genetics can influence risk and severity, but kissing spines is still best understood as a multifactorial condition. Genetics may load the gun, but conformation, height, training, saddle fit, core strength, lameness, posture, workload, and management may all help pull the trigger.

Quick Answer

Kissing spines in horses can have a hereditary component, but it is not proven to be a simple single-gene disease. Early AAEP-reported research suggested regions on chromosomes 14, 16 and 25 may influence whether kissing spines develops and how severe it becomes, while a later published genome-wide association study found two significant markers on chromosome 25 associated with increased kissing spine grade in stock-type and Warmblood horses. Further research is still needed before genetic testing should be used as a stand-alone breeding, purchase, or career decision tool. (The Horse)

What Are Kissing Spines?

Kissing spines, more formally called overriding or impinging dorsal spinous processes, occur when the bony projections along the top of the vertebrae sit too close together, touch, or overlap. These projections are called dorsal spinous processes. When the space between them narrows, the area can become inflamed, painful, or mechanically irritated. (Center for Equine Health)

Kissing spines most commonly affects the thoracic spine, especially the region under the saddle and rider. UC Davis notes that the condition is commonly found between T13 and T18, with T15 often affected, although lumbar involvement can occur less commonly. (Center for Equine Health)

The important clinical point is that kissing spines on X-rays does not automatically mean the horse has back pain. UC Davis notes that many horses with kissing spines do not show clinical signs, and that imaging findings do not always correlate neatly with pain or performance problems. (Center for Equine Health)

That is where owners can get caught. An X-ray can show the bones are close together. It does not, by itself, prove that the horse’s behaviour, bucking, lameness, or poor performance is caused by those bones.

Is Kissing Spines Hereditary?

The best answer is: partly, in some horses, but it is not the whole story.

Research has found evidence that genetic regions may influence the risk or severity of kissing spines. Early AAEP-reported research described regions on chromosomes 16 and 25 that appeared to affect severity in Warmbloods, Thoroughbreds, and stock horse breeds, while chromosome 14 was reported as being associated with whether the disease was present or absent. (The Horse)

A later published study in Research in Veterinary Science examined 155 stock-type and Warmblood horses using clinical and radiographic grading from 0 to 4. That study found two significantly associated SNPs on chromosome 25, and the best-associated marker was linked with an average increase of one kissing spine grade per A allele in that study population. (Mad Barn USA)

That sounds exciting, and it is. But it does not mean we can say, “This horse has the gene, therefore it will get kissing spines.”

The researchers themselves described the results as preliminary and called for further work in other breeds and larger populations. They also proposed more research to identify causative variants and test whether the chromosome 25 marker behaves the same way in other horse populations. (Mad Barn USA)

So the practical veterinary answer is this:

• Kissing spines can have inherited risk.

• Genetics may influence severity.

• Some breeds and body types appear overrepresented.

• A genetic marker is not the same as a guaranteed diagnosis.

• X-rays, clinical signs, pain response, saddle fit, training, and lameness workup still matter.

What Did the Genetics Research Actually Find?

This is where the wording needs to be careful.

The early report presented at the 2020 AAEP Convention suggested:

• Chromosome 14 may be associated with presence or absence of kissing spines.

• Chromosome 16 may affect severity by about one grade.

• Chromosome 25 may affect severity by about two grades.

• Height appeared to have a strong impact.

• Sex and age appeared less influential than previously thought. (The Horse)

The later published study was more specific. It found:

• 155 stock-type and Warmblood horses were examined.

• Horses were graded from 0, meaning unaffected controls, to 4, meaning severe kissing spines.

• A genome-wide association study was performed.

• Two significant SNPs were found on chromosome 25.

• One marker, BIEC2-668062, was associated with an average increase of one kissing spine grade per A allele in that population.

• Breed group, age, height, and sex were not statistically significant in that study population. (Mad Barn USA)

The difference matters. Early conference findings are useful, but the published paper is the stronger scientific reference. For an owner or breeder, the safest interpretation is that there is evidence of genetic influence, especially involving chromosome 25, but kissing spines is not yet a simple genetic yes-or-no condition.

Which Horses Are Most at Risk?

Kissing spines can affect any breed, but some groups appear overrepresented.

The American College of Veterinary Surgeons notes that Thoroughbreds and Warmblood-type horses tend to be overrepresented, although horses of any breed can be affected. (American College of Veterinary Surgeons)

The published genetics study focused on stock-type and Warmblood horses, and the abstract notes that Thoroughbreds, Warmbloods, Paint Horses, Quarter Horses, and other stock-type breeds are considered at increased risk of developing clinical signs. (Mad Barn USA)

Risk may be influenced by:

• Breed

• Height

• Conformation

• Back shape

• Saddle fit

• Training style

• Core strength

• How the horse carries its head and neck

• Rider weight and balance

• Workload

• Lameness elsewhere

• Previous injury

• Genetic background

UC Davis notes that kissing spines are likely acquired in many horses and can be influenced by factors such as poor saddle fit and training that allows the horse to move with the head up, hollow back, and poor core engagement. (Center for Equine Health)

In practice, this is rarely one neat cause. It is usually a stack of risk factors. The horse does not read the textbook. The horse simply presents the bill.

What Are the Signs of Kissing Spines?

Clinical signs can be subtle, inconsistent, or dramatic.

Possible signs include:

• Back soreness when groomed or palpated

• Bucking under saddle

• Rearing

• Head tossing

• Kicking out

• Girthiness

• Hollowing the back

• Resistance to the bit

• Difficulty with transitions

• Cross-cantering

• Refusing or rushing fences

• Reduced impulsion

• Poor performance

• Reluctance to collect

• Difficulty bending

• Behaviour changes when saddled

• Vague or overt lameness

UC Davis and ACVS both note that signs vary widely, from no clinical signs at all to significant discomfort and poor performance. (Center for Equine Health)

The Retired Racehorse Project also highlights that some horses show obvious back sensitivity, while others show more ridden signs such as travelling hollow, struggling with transitions, refusing jumps, or difficulty turning around barrels. (Retired Racehorse Project)

A key clinical point: kissing spines can mimic training problems, behavioural issues, saddle-fit problems, ulcers, hindlimb lameness, sacroiliac pain, hock pain, and poor conditioning.

That is why diagnosis needs more than one X-ray.

Does Every Horse With Kissing Spines Have Pain?

No.

This is one of the most important parts of the whole article.

A horse can have radiographic kissing spines and still appear comfortable, trainable, rideable, and clinically normal. UC Davis notes that many horses with kissing spines do not show clinical signs, and that the true incidence of pain directly attributable to kissing spines has not been established. (Center for Equine Health)

The Retired Racehorse Project discusses a study where 68% of horses with clinical back pain had kissing spines on radiographs, but 39% of horses with no back pain history or clinical back pain also had radiographic kissing spines. That means radiographs matter, but they are not the entire diagnosis. (Retired Racehorse Project)

This is where veterinary judgement matters. The question is not just “are the bones close?” The question is:

Do the clinical signs, exam findings, response to local anaesthesia, imaging findings, and work history all point to kissing spines as the pain source?

How Worried Should You Be?

Kissing spines ranges from incidental to career-limiting.

Low Concern

This is more likely when:

• Kissing spines are found incidentally on X-rays.

• The horse has no back pain.

• Performance is normal.

• The horse is comfortable under saddle.

• There is no lameness or behavioural change.

• Saddle fit is good.

• Core strength and topline are appropriate.

Action: do not panic. Monitor, maintain good conditioning, keep saddle fit checked, and avoid assuming the horse is broken because of an X-ray finding.

Moderate Concern

This is more likely when:

• The horse has back sensitivity.

• Performance has dropped.

• The horse resists collection or transitions.

• Signs appear under saddle but not always in hand.

• There are mild radiographic changes.

• Saddle fit, training, or muscle weakness may contribute.

Action: book a veterinary exam, assess saddle fit, review training, check for lameness elsewhere, and start a structured rehab plan if kissing spines are clinically relevant.

High Concern

This is more likely when:

• The horse bucks, rears, kicks out, or becomes unsafe under saddle.

• The horse has clear back pain on palpation.

• Radiographs show more severe impingement or multiple affected spaces.

• Pain improves after diagnostic local anaesthetic infiltration.

• There is concurrent lameness.

• Conservative care has failed.

Action: stop ridden work until assessed. A full lameness and back workup is needed. Treatment may include injections, shockwave, medication, rehabilitation, and possibly surgical discussion.

Critical Concern

Kissing spines itself is not usually a sudden life-threatening emergency, but the signs around it can become urgent.

Treat the situation as urgent if:

• The horse becomes suddenly dangerous under saddle.

• There is sudden severe lameness.

• The horse falls, collapses, or shows neurological signs.

• There is marked incoordination.

• There is severe pain, fever, trauma, or inability to move normally.

• You suspect fracture, spinal trauma, or neurological disease.

Action: stop riding immediately and call your vet.

When Is Back Pain an Emergency?

Back pain or behaviour under saddle needs urgent veterinary attention if your horse has:

• Sudden severe pain

• Incoordination

• Weakness

• Collapse

• Loss of tail tone

• Urinary or faecal issues

• Severe lameness

• Trauma or fall

• A horse that becomes unsafe to handle

• Neurological signs

• Rapid worsening over hours or days

• Fever or systemic illness

Kissing spines usually develops as a chronic performance or back pain problem, but not every painful back is kissing spines. Trauma, neurological disease, pelvic injury, fracture, severe lameness, and systemic illness must be considered when signs are sudden or severe.

What Else Can Look Like Kissing Spines?

This is where many owners lose months.

A horse that bucks, resists, or hollows under saddle does not automatically have kissing spines. Even if X-rays show kissing spines, another condition may be the main pain source.

Important rule-outs include:

Poor Saddle Fit

A saddle that pinches, bridges, rocks, or places pressure over the thoracic spine can cause back pain and behavioural signs.

Hindlimb Lameness

Hock pain, stifle pain, suspensory pain, or foot pain can make the horse protect itself through the back. ACVS notes that lameness can incite or exacerbate back pain and may even be the presenting complaint. (American College of Veterinary Surgeons)

Sacroiliac Pain

Sacroiliac region pain can cause poor impulsion, canter problems, resistance, and back soreness.

Gastric Ulcers

Ulcers can cause girthiness, resentment to work, poor performance, and behaviour changes.

Poor Core Strength

Weak abdominal and back stabilising muscles can make a horse move hollow, especially under rider weight.

Training and Rider Factors

A horse consistently ridden in a hollow frame, with poor balance, tension, or forced collection before strength is developed, may become sore through the back.

Neck, Pelvic, or Limb Pain

Pain elsewhere can change posture and loading patterns through the spine.

Behavioural or Learned Responses

Pain may start the behaviour, but the pattern can persist even after pain improves. That does not mean the horse is “naughty.” It means behaviour, fear, memory, and pain can become tangled.

How Do Vets Diagnose Kissing Spines?

A proper diagnosis combines clinical signs, physical examination, imaging, and sometimes response to diagnostic treatment.

A typical workup may include:

• Detailed history

• Ridden history and performance changes

• Physical examination

• Back palpation

• Muscle symmetry assessment

• Saddle-fit review

• Lameness evaluation

• Assessment on the lunge

• Ridden assessment if safe

• Radiographs of the spine

• Ultrasound in selected cases

• Local anaesthetic infiltration around suspected painful spaces

• Scintigraphy or advanced imaging in selected cases

ACVS notes that diagnosis can be difficult because signs are vague and varied. A full lameness evaluation is often performed, and diagnostics may include radiographs, ultrasound, local anaesthesia of suspected painful sites, and nuclear scintigraphy in difficult cases. (American College of Veterinary Surgeons)

UC Davis also emphasises that radiographs are commonly used, but diagnosis should not rely on X-rays alone. Clinical examination and the whole picture matter. (Center for Equine Health)

Why X-Rays Alone Are Not Enough

X-rays can show narrowed spaces, touching spinous processes, overriding processes, sclerosis, remodelling, or other bony changes.

But X-rays cannot answer every question.

They do not always tell you:

• Whether the horse is painful today

• Whether the finding is incidental

• Whether another lameness is driving the back pain

• Whether saddle fit is the real trigger

• Whether the horse can return to work

• Whether surgery is needed

• Whether the horse should never be ridden again

ACVS specifically notes that radiographic abnormalities must be interpreted with the whole clinical picture, because many horses have radiographic changes without clinical signs of back pain. (American College of Veterinary Surgeons)

The strongest diagnosis comes when multiple pieces match:

• The horse has compatible signs.

• The painful area matches the imaging.

• Other causes have been considered.

• Local anaesthetic improves the signs.

• Treatment and rehab lead to measurable improvement.

Can Genetic Testing Diagnose Kissing Spines?

Genetic testing may help identify risk in some horses, but it should not replace veterinary diagnosis.

The published GWAS supports chromosome 25 as a candidate region associated with severity in the studied stock-type and Warmblood population. The authors described the findings as preliminary and recommended further research in other breeds and populations. (Mad Barn USA)

So genetic testing should be viewed as a risk tool, not a diagnosis tool.

A horse with a risk marker may never develop painful kissing spines.

A horse without a known marker can still develop back pain.

A horse with radiographic kissing spines may be pain-free.

A horse with back pain may have a different primary cause.

That is the annoying but clinically honest answer. Genetics can help the conversation. It cannot replace the exam.

Should Horses With Kissing Spines Be Bred?

This is where the article needs to be blunt.

Breeding from a horse with clinically significant kissing spines deserves serious caution, especially if the horse retired early or became performance-limited because of back pain.

The early AAEP-reported article quoted researchers advising owners to seriously consider not breeding horses with kissing spines, especially horses retired because of performance issues, because doing so may perpetuate the problem. (The Horse)

That does not mean every horse with an incidental X-ray finding should automatically be removed from breeding. But if the horse has:

• Clinical back pain

• Severe radiographic kissing spines

• Multiple affected spaces

• Performance-limiting disease

• A family history of kissing spines

• Early retirement due to back pain

• Confirmed genetic risk markers, where tested

• Offspring with similar issues

Then breeding becomes difficult to justify from a welfare and long-term soundness perspective.

A good breeding decision should consider the whole horse: health, performance history, conformation, temperament, veterinary findings, family history, genetic information, and the risk of producing foals predisposed to pain.

How Are Kissing Spines Treated?

Treatment depends on whether kissing spines are actually causing pain and how severe the case is.

Treatment is usually multimodal. ACVS notes that long-term management often relies on stretching and strengthening the back and core muscles, pain management, local treatments, and sometimes surgery. (American College of Veterinary Surgeons)

Common treatment options include:

Rehabilitation and Core Strengthening

This is the foundation for many cases.

Rehab may include:

• Long and low work

• In-hand stretching

• Pole work

• Hill work, where appropriate

• Controlled lunging

• Walking programs

• Cavaletti work

• Gradual topline strengthening

• Physiotherapy-guided exercises

• Correct posture and core engagement

UC Davis notes that physical therapy may include exercises to encourage the horse to move in a relaxed frame, then progress to poles, cavaletti, resistance systems, and aqua treadmill work where appropriate. (Center for Equine Health)

Saddle Fit Correction

Saddle fit must be checked. A horse with kissing spines and poor saddle fit is being asked to do maths while someone pokes them in the ribs.

UC Davis includes saddle fit assessment as part of treatment to reduce pressure points on the back. (Center for Equine Health)

Pain Relief and Medical Therapy

Medical management may include:

• NSAIDs in selected cases

• Muscle relaxants

• Shockwave therapy

• Mesotherapy

• Corticosteroid injections around affected spaces

• Local anti-inflammatory treatment

• Manual therapy, acupuncture, or chiropractic care as part of a vet-led plan

UC Davis lists shockwave therapy, mesotherapy, corticosteroid injections between vertebrae, chiropractic, acupuncture, therapeutic ultrasound, and laser therapy as options used in management. (Center for Equine Health)

Diagnostic and Therapeutic Local Anaesthesia

Local anaesthetic can help confirm whether the suspected kissing spine region is actually contributing to pain. EquiManagement reported that in an international survey of equine orthopedic specialists, 73% used local anaesthesia to aid diagnosis. (EquiManagement)

This matters because radiographs and ultrasound are not always defining. EquiManagement notes that many practitioners rely on diagnostic local anaesthetic infusion between affected spinous processes to guide interpretation. (EquiManagement)

Surgery

Surgery may be considered when conservative management fails or the case is severe.

Common procedures include:

• Interspinous ligament desmotomy

• Partial ostectomy of affected dorsal spinous processes

• Endoscopic removal of selected bone in some cases

ACVS describes interspinous ligament desmotomy and dorsal spinous process ostectomy as surgical options, with similar overall success reported between approaches. (American College of Veterinary Surgeons)

UC Davis notes that surgery can produce positive results, but surgical approaches can also destabilise the back and may lead to future lameness, so case selection and rehabilitation are critical. (Center for Equine Health)

What Is the Prognosis?

Many horses with clinically relevant kissing spines can improve, but the outcome depends on severity, how many spaces are involved, whether there are other pain sources, and whether rehabilitation is done properly.

UC Davis notes that most affected horses with clinical signs can return to work with medical or surgical treatment and physical therapy, but sustained results often require a multifaceted approach and commitment from the horse’s caregivers. It also notes a poorer prognosis in horses 5 years old or younger, horses with five or more vertebrae involved, and cases secondary to other spinal issues. (Center for Equine Health)

The Retired Racehorse Project similarly notes that many horses can do well and return to previous work, but prognosis decreases in horses under 5 and horses with more than five vertebrae involved. (Retired Racehorse Project)

In practice, the best outcomes usually happen when:

• The diagnosis is accurate.

• Other lameness is addressed.

• Saddle fit is corrected.

• The horse is not rushed.

• Rehab is consistent.

• The owner understands this is not fixed by one injection and a hopeful pat.

What Should You Do If You Suspect Kissing Spines?

1. Stop Blaming the Horse

Bucking, resistance, and poor performance may be behavioural, but pain should be ruled out before the horse is labelled difficult.

2. Record What You Are Seeing

Useful details include:

• When signs started

• Whether signs are sudden or gradual

• Whether they occur under saddle only

• Which rein is worse

• Whether transitions are affected

• Whether jumping, collection, canter, or lateral work triggers signs

• Whether grooming, girthing, mounting, or saddling causes a reaction

3. Check Saddle Fit

Do not skip this. A saddle-fit issue can worsen kissing spines or mimic it.

4. Book a Veterinary Workup

Ask for a proper exam, not just back X-rays. The horse may need a lameness workup, back palpation, imaging, and possibly local anaesthetic testing.

5. Do Not Rush to Surgery

Surgery has a place, but many horses start with rehabilitation, pain management, saddle-fit correction, and controlled strengthening.

6. Build the Back Slowly

Rehab is not “a few carrot stretches and vibes.” It needs structure, progression, and reassessment.

7. Think Carefully Before Breeding

If kissing spines are clinically significant, severe, performance-limiting, or present in related horses, breeding should be approached very cautiously.

Common Mistakes Owners Make

Assuming Every X-Ray Finding Is Painful

Kissing spines can be incidental. Treat the horse, not just the image.

Assuming Behaviour Means Bad Attitude

Pain and learned behaviour can look similar under saddle. Rule out pain first.

Skipping the Lameness Workup

A horse with hock, stifle, foot, or sacroiliac pain can develop secondary back pain.

Injecting Without Rehabilitation

Injections may reduce pain, but without strengthening and posture work, the horse may relapse.

Ignoring Saddle Fit

A poorly fitting saddle can undo even the best treatment plan.

Breeding a Performance-Limited Horse Without Thinking Hard

If the horse retired because of clinically significant kissing spines, breeding may pass risk into the next generation.

Can Kissing Spines Be Prevented?

Not every case can be prevented, especially where conformation or genetic risk plays a role. But good management may reduce clinical problems.

Practical prevention and risk reduction include:

• Correct saddle fit

• Regular saddle checks as the horse changes shape

• Gradual fitness development

• Core strengthening

• Avoiding forced collection before strength is developed

• Encouraging correct posture and topline

• Managing lameness early

• Maintaining hoof balance

• Avoiding excessive rider weight for the horse’s build

• Varying work

• Including hacking, hills, poles, and controlled conditioning where appropriate

• Avoiding repetitive high-impact work in weak or painful horses

• Monitoring young performance horses carefully

• Making ethical breeding choices

UC Davis notes that possible underlying contributors such as lameness and improper saddle fit should be addressed because these may prevent horses from using their backs properly. (Center for Equine Health)

Myth vs Reality

Myth	Reality
Kissing spines always causes pain.	Many horses have radiographic changes without obvious clinical signs.
It is purely genetic.	Genetics may contribute, but training, saddle fit, posture, lameness, height, conformation, and workload also matter.
A genetic marker means the horse will definitely get it.	Current markers suggest risk, not certainty.
X-rays alone diagnose the problem.	X-rays show anatomy. The clinical exam determines whether the finding matters.
Surgery is the only real treatment.	Many cases start with rehab, saddle fit, pain management, strengthening, and controlled exercise.
A horse with kissing spines should always be retired.	Some horses return to useful work with correct diagnosis and management.

FAQs About Hereditary Kissing Spines in Horses

Is kissing spines definitely hereditary?

There is evidence of a hereditary component, but kissing spines is not a simple single-gene disease. Research has identified genetic regions associated with risk or severity, especially chromosome 25 in a published study, but management, conformation, height, training, saddle fit, lameness, and core strength also matter. (Mad Barn USA)

Should I breed a horse with kissing spines?

Be very cautious, especially if the horse has clinical pain, severe radiographic changes, multiple affected spaces, early retirement, or performance-limiting back pain. Breeding from clinically affected horses may perpetuate the problem. (The Horse)

Can a horse have kissing spines and no symptoms?

Yes. Many horses have radiographic kissing spines without obvious clinical signs. The diagnosis only becomes meaningful when the imaging findings match the horse’s clinical signs, pain response, and work history. (Center for Equine Health)

Can kissing spines be treated without surgery?

Yes. Many horses are managed with rehabilitation, saddle-fit correction, controlled strengthening, local injections, shockwave, physiotherapy, and other medical therapies. Surgery is usually considered when conservative treatment fails or the case is severe. (Center for Equine Health)

Is genetic testing enough to diagnose kissing spines?

No. Genetic testing may help identify risk in some horses, but it does not replace a veterinary exam, lameness workup, imaging, diagnostic anaesthesia, and clinical judgement. Current research is still developing. (Mad Barn USA)

The Bottom Line

Kissing spines in horses can be hereditary, but it is not just hereditary.

The best current interpretation is that genetics may increase risk or severity, particularly in some breeds and populations, but the condition is shaped by many other factors: conformation, height, saddle fit, training, posture, workload, core strength, pain elsewhere, and overall management.

For owners, the key is not to panic over an X-ray finding and not to ignore a painful horse. For breeders, the key is to think long term. A horse that was genuinely limited by kissing spines may not be the right candidate to pass those risks forward.

The smartest approach is balanced: diagnose properly, treat the whole horse, rehabilitate carefully, and make breeding decisions with welfare at the centre.

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If your horse has back pain, poor performance, or possible kissing spines and you are unsure how serious it is, ASK A VET™ can help you organise the signs, understand what matters, and decide when a hands-on veterinary workup is needed.