Kissing spine in horses: the signs riders notice, and what the X-ray does and doesn't tell you

Kissing spine is when the bony spikes on top of a horse’s vertebrae, the dorsal spinous processes, sit too close together and touch or overlap. It can cause back pain that shows up as bucking, hollowing, a cold back or reluctance to work. But many horses with it on an X-ray are not in pain at all.

A “kissing spine” diagnosis can sound like the end of a horse’s ridden career. In reality the X-ray is only one part of the picture, and the horse in front of you, under saddle, is the part that matters. This post covers the signs, what else they can be, diagnosis, treatment, and whether you can keep riding.

What is kissing spine in horses?

Each vertebra along a horse’s back has a bony projection pointing upwards, called the dorsal spinous process. Normally there is a gap between one and the next. In kissing spine, also called overriding or impinging dorsal spinous processes, that gap narrows and the processes touch or overlap.

A 2025 review of the research in the journal Animals defines it as narrowing of the space between them to less than 4mm, with touching or overlapping. It mostly affects the middle and back end of the thoracic spine, the vertebrae known as T13 to T18, which sits roughly under the back of the saddle. T15 is the one most often involved, and the lumbar spine can be affected too. Warmbloods, Thoroughbreds and Quarter Horses seem particularly prone.

What are the symptoms of kissing spine in horses?

The signs are vague, and most show up in the ridden work rather than in the field. The review lists:

• Resistance to grooming or saddling, the classic cold-backed horse that dips or fidgets as the saddle goes on
• A stiff, braced back when ridden
• Poor engagement from behind, or a horse that has lost its jumping technique
• Trouble holding canter, or reluctance to bend or work in one direction
• Reluctance to work, or a general drop in performance

Riders also describe bucking, hollowing, napping, rushing, and behaviour changes such as a horse that pins its ears or swishes its tail when tacked up. Girthiness is common.

None of these is specific to kissing spine. Every one has other causes, some of them more common.

The saddle slip line has research behind it. In a study of 128 horses at the Animal Health Trust in Newmarket, the saddle consistently slipped to one side in 54% of horses with hind-limb lameness, and in none of the 20 horses with back pain or sacroiliac pain. When nerve blocks took the lameness away, the slip stopped in 37 of 38 horses.

Back pain and hind-limb lameness are tangled up with each other, and pain in one often looks like pain in the other. Our guide on how to tell if your horse is lame behind covers what to watch for from the ground, and if canter is the sticking point, see why a horse won’t canter on one lead.

What are mild kissing spine symptoms in horses?

Mild back pain rarely looks dramatic. It tends to be the horse that is “not quite right”: a bit flat, slower to warm up, less willing in canter, or swishing its tail more than it used to.

One useful tool here is the Ridden Horse Pain Ethogram, developed by Dr Sue Dyson and colleagues. It is a list of 24 behaviours, such as ears flat for five seconds or more, an intense stare, repeated tail swishing, tongue out, bucking and spontaneous changes of gait. In a paper applying it to 60 sports and riding school horses, a score of 8 or more out of 24 was a good indicator of musculoskeletal pain.

That same study is a sobering read. Every horse was assumed by its owner to be working comfortably, and 73% were lame on one or more limbs. Mild pain is easy to miss when you ride the horse every day. The ethogram doesn’t say where the pain is, but it is a good reason to film a schooling session and watch it back.

Does a horse with kissing spine on an X-ray always have back pain?

No, and this is the single most useful thing to know about kissing spine.

The 2025 review reports that radiographic and post-mortem studies have found the condition in up to 92% of horses, and that not all horses with these changes show clinical signs. It also notes that some abnormal findings on back X-rays turn up in horses that are performing normally, and that there is no agreed cut-off grade separating a sound horse from a sore one.

A large UK study backs this up while adding a twist. Researchers at the Animal Health Trust examined 582 horses presented for back pain or poor performance. Worse X-ray grades were linked to back pain, so the images do mean something. But lameness in the front or hind legs, or sacroiliac pain, could mimic primary back pain, and the authors concluded that diagnostic analgesia, meaning nerve blocks, is crucial for an accurate diagnosis.

So kissing spine on the pre-purchase X-ray of a horse that goes beautifully is a conversation with the vet, not an automatic fail. And in a sore horse, finding it doesn’t prove it is the cause.

What causes kissing spine in horses?

Nobody fully knows. The review describes the cause as complex and multifactorial. Most of the research suggests it is acquired over a horse’s life rather than present at birth: an X-ray study of Warmblood foals found no narrowing up to three months old.

Factors that have been proposed include:

• Age, sex and breed
• Conformation, such as a short back or particular shapes of spinous process
• How the back moves in work, since the caudal thoracic spine is the most mobile part
• Saddle fit and rider pressure, through repeated trauma and inflammation

Newer work found a link with a genetic variant, and one author reported similar rates in untrained Thoroughbred yearlings and adult horses, so for some horses it may begin young. Saddle fit is the factor most within your control.

How is kissing spine diagnosed?

A back workup is a process of elimination. The review describes the usual steps:

1. A look at the back: conformation and muscling either side of the spine.
2. Palpation and passive mobilisation, pressing along the back and encouraging the horse to flex, extend and bend.
3. Watching the horse move: walking a figure of eight, trotting in a straight line, lungeing on both reins on hard and soft ground, and cantering.
4. Ruling out lameness, so the back is confirmed as the main problem.
5. Seeing the horse ridden.
6. Imaging: X-rays of the spinous processes, often with ultrasound, and sometimes a bone scan (scintigraphy) at a referral hospital.
7. Nerve blocks, injecting local anaesthetic around the suspect spaces to see whether the horse moves or behaves better.

The review notes that back blocks are harder to read than leg blocks, because the anaesthetic spreads and can change how the back moves even in a sound horse, so your vet weighs them alongside everything else.

What is the treatment for kissing spine in horses?

The options fall into three groups, and most horses get a combination:

• Rest and controlled rehab, rebuilding the muscles that support the back
• Medication, most often injections into or around the affected spaces to calm inflammation, and sometimes other drugs given by your vet
• Surgery, either removing part of the affected spinous processes or cutting the ligament between them (interspinous ligament desmotomy), both of which have been done with the horse standing under sedation

There is no single agreed approach. In an international survey of 353 equine orthopaedic specialists, 71% preferred conservative management and recommended surgery only for horses that didn’t respond. The most popular combination was local injection with controlled exercise. Specialists in the UK, Ireland and the US were the most likely to recommend surgery as a first step.

Whichever route your vet suggests, the review sums up the goal as breaking the pain cycle so the horse can rebuild its core strength. Pain can stop a horse using the deep muscles that stabilise the spine, so they waste, and the back becomes less stable and more sore. Treatment buys you a window. The rehab is what fills it.

How long does kissing spine surgery recovery take?

It depends on the procedure, the horse and your vet’s plan, so take your surgeon’s timeline over anyone else’s. For a sense of what published work shows, a UK study of 68 horses at Cotts Equine Hospital in Pembrokeshire compared steroid injections with standing desmotomy surgery. All the horses followed the same controlled exercise plan and returned to work three to six weeks after treatment.

Both groups did well at first: back pain initially resolved in 89% of the medically treated horses and 95% of the surgical ones. The difference came later. Back pain came back in 19 of the medical cases and in none of the surgical ones.

Returning to work is not the same as full fitness. Our guide to getting a horse fit after time off covers how to structure the weeks.

Can you ride a horse with kissing spine?

Often, yes, but on your vet’s say-so and with the pain dealt with first.

Plenty of horses carry kissing spine changes on X-ray and are ridden happily for years, because the changes alone are not always painful. And for horses that are sore, controlled exercise is part of nearly every treatment plan, ridden and in hand. In the Cotts Equine Hospital study, every horse went back to work on a set exercise plan within six weeks.

What you shouldn’t do is keep riding a horse that is showing pain and hope it works through it. A horse that bucks every time you ask for canter is telling you something, and riding it harder risks a fall. Get a diagnosis, treat the pain, then build back up slowly with a plan your vet agrees.

Have a qualified saddle fitter check the saddle before your horse goes back into work, because a back that has lost or is rebuilding muscle may need a different fit.

When should you call the vet about a horse’s back?

Back pain is rarely an emergency, but it shouldn’t be left to drift. Book a vet visit if:

• A change in ridden behaviour lasts more than a few rides, especially new bucking, napping or refusing
• Your horse is suddenly cold-backed or girthy when it never used to be
• The saddle has started slipping to one side
• Your horse seems stiff, lame or uneven, even slightly

Call the same day if your horse is in obvious pain, cannot get up or move normally, or has had a fall or a heavy knock to the back.

Where the technology fits

Stride can’t diagnose kissing spine, read an X-ray, or score the Ridden Horse Pain Ethogram. What it can do is help you notice a pattern sooner and show your vet dates rather than impressions.

• Ride behaviour tags. After a ride you can tag how the horse went: Good as gold, Fresh / strong, Spooky, Nappy / reluctant, Tense / tight, Bucky or Felt off, and mark whether you fell off.
• A Ride Behaviour flag. The app looks at a horse’s last 12 rides. If any were tagged Tense, Nappy, Bucky, Spooky or Felt off, or you fell off, it raises a flag (two or more reads as unsettled) and suggests ruling out discomfort, including tack fit, back, teeth, feet and soundness. It is a nudge to look, not a diagnosis.
• Observations. A fixed list of things you noticed, including Stiff, Girthy, Lame and Reluctant to work, each with an optional mild, moderate or marked rating and a note. There is no field for where on the body, so write “dipped when saddled” in the note.
• Ride tracking. GPS records distance, time, speed, climb and an estimated breakdown of time in each gait from speed. It is an estimate, and it can’t spot a back problem or lameness.
• Vet records with attachments. You can add photos or a PDF, such as the vet’s report, to a vet record so it sits on the horse’s timeline.
• Bodywork reminders, alongside vet, farrier, dental and the rest, for physio follow-ups.

The diagnosis stays with your vet.

If you take one thing from this: a kissing spine X-ray is not a verdict, and a horse that is bucking or cold-backed is not “just being naughty”. Write down what you notice under saddle, with dates, for a fortnight. Then get your vet to look at the whole horse, legs included, before anyone decides what the back is telling you.