Preventing kissing spine in horses comes down to building strong core muscles, fitting tack properly, managing rider weight, and introducing work at the right pace for a young horse’s developing skeleton. While some horses may have a genetic predisposition, the condition is heavily influenced by how a horse is trained, ridden, and managed throughout its life.
Kissing spine occurs when the bony projections on top of the vertebrae get too close together (less than 4 mm apart) and begin touching or overlapping. It most commonly affects the middle and rear thoracic vertebrae, particularly T13 through T18, with T15 being the single most affected site. That location sits directly under the saddle and the rider’s seat, which makes training, saddle fit, and rider balance central to prevention.
Why Core Strength Matters Most
A horse’s back doesn’t hold itself up passively. The muscles running along the spine and underneath the abdomen act like a suspension bridge, keeping the vertebrae properly spaced while carrying the weight of a rider. When those muscles are weak or underdeveloped, the spine sags, the spaces between the spinous processes narrow, and the conditions for kissing spine develop. Building and maintaining core strength is the single most effective thing you can do to protect your horse’s back.
Two types of exercises are particularly useful, and both can be done during groundwork:
- Belly lifts: Apply gentle pressure under the horse’s abdomen to encourage it to lift and round its back. This engages the deep stabilizing muscles along the spine. You can do this while the horse is standing still or walking.
- Baited stretches (carrot stretches): Use a treat to guide the horse’s head and neck in different directions, holding each position for two to three seconds. These activate the core muscles that support the thoracic and lumbar spine. Guide the horse to reach between its front legs, toward each hip, and toward each stifle for a full range of engagement.
Under saddle, transitions between gaits are one of the best core builders. Frequent walk-to-trot and trot-to-canter transitions ask the horse to shift its balance and engage its topline repeatedly. Hill work, ground poles, and cavaletti also encourage the horse to lift its back and use its core. The key is variety. Drilling a horse in one frame or one gait for long stretches does less for spinal health than mixing things up.
Get Saddle Fit Right
A poorly fitting saddle concentrates pressure on the exact vertebrae most vulnerable to kissing spine. Research on how the equine back moves during walk and trot shows that the least-mobile part of the back sits in the thoracic region, which is where a well-fitted saddle tree should rest. The more mobile areas, especially around the withers, need to be left free.
A few specific guidelines stand out from the science:
- Clearance over the withers: The saddle pommel should sit well above the withers. With a rider seated, clearance should exceed 25 mm. The withers area is highly mobile, and compression here can cause pain and compensatory movement that stresses the rest of the spine.
- Don’t extend past T18: Standard saddle-fitting practice recommends that the saddle tree should not reach beyond the 18th thoracic vertebra. Saddles that sit too far back encroach on the more mobile lumbar region.
- When in doubt, place it slightly back rather than forward: Research suggests that a saddle positioned slightly too far back causes less tissue impingement than one pushed too far forward onto the withers.
- Distribute pressure broadly: A rigid saddle tree that covers more of the low-mobility thoracic region spreads pressure over a larger area and reduces focal high-pressure points. This is why a well-fitted tree matters more than extra padding.
Have your saddle evaluated by a qualified fitter at least once a year, and again any time your horse’s body condition changes significantly. A saddle that fit perfectly in spring may not fit in fall if the horse has gained or lost muscle.
Rider Weight and Balance
Rider size affects the horse’s back more than many owners realize, and it isn’t just about the number on the scale. A study testing horses with riders of varying weights found substantial adverse effects on gait and behavior from heavier riders, with none of the heavy or very heavy riders able to complete the full set of movement tests. Interestingly, rider BMI alone wasn’t the deciding factor. A moderately overweight rider with good balance completed nearly all tests, while a heavier rider could not.
This points to something important: rider position, balance, and coordination matter as much as raw weight. A rider who sits crookedly, braces against the horse, or bounces at the trot creates uneven, repetitive impact on the thoracic spine. Improving your own fitness, core stability, and riding position is a direct investment in your horse’s spinal health. Regular lessons focused on your seat, even for experienced riders, pay dividends.
There’s no single universally accepted rider-to-horse weight ratio, because so many factors interact: the horse’s fitness, muscle development, back length, age, the speed and duration of work, and the terrain. But the principle is straightforward. Keep the total load reasonable for your horse’s build, and make sure you’re carrying yourself well in the saddle rather than being a passive weight the horse has to brace against.
Starting Young Horses Safely
How and when you introduce a young horse to ridden work shapes its spinal health for years. A horse reaches 90% of its mature height by 12 months but doesn’t finish growing until around age four. The temptation to start serious riding work early can be strong, but the developing skeleton needs the right kind of loading at the right time.
The relationship between early exercise and skeletal health is more nuanced than “wait until they’re older.” Research on young Thoroughbreds found that horses with still-open growth plates that were exposed to training actually had a lower incidence of lameness than horses whose growth plates had already closed. Inactivity can be detrimental to growth plate health, because dynamic loading during development helps optimize bone strength through maturity. The same principle applies to tendons: exposure to appropriate exercise during growth produces stronger connective tissue at maturity.
The practical takeaway for preventing kissing spine is to build a foundation of movement and strength before adding the weight and demands of a rider. Groundwork, lunging at appropriate levels, free movement in varied terrain, and the core exercises described above all prepare the young horse’s musculoskeletal system. When you do begin ridden work, keep sessions short, prioritize balance and relaxation over collection or speed, and increase intensity gradually over months rather than weeks.
Recognizing Early Warning Signs
Prevention also means catching problems before they become entrenched. Kissing spine doesn’t appear overnight, and horses often show subtle behavioral changes long before the condition becomes severe. Knowing what to watch for lets you adjust your management before real damage is done.
Common early signals include resistance to girthing (flinching, biting, or swinging away when you tighten the cinch), reluctance to transition between gaits, a stiff or hollow back under saddle, difficulty bending, and general irritability during grooming or tacking up. Some horses begin refusing jumps, bucking during canter departures, or simply losing impulsion. These behaviors are often dismissed as attitude problems, but they frequently point to back pain.
If you notice a pattern of these signs, a veterinary evaluation of the thoracic spine is worthwhile. Imaging can reveal narrowing of the interspinous spaces before the processes actually begin overlapping, giving you a window to intervene with targeted exercise, tack adjustments, and workload changes rather than more invasive options down the road.
Turnout and Daily Movement
Horses evolved to move almost constantly, and prolonged stall confinement works against spinal health. Standing still for hours allows the muscles supporting the back to weaken and stiffen. Regular turnout, ideally on varied terrain, encourages the horse to use its body naturally, engaging its core and topline without the added load of a rider. Even on days off from training, free movement in a pasture or paddock supports the spine more than standing in a stall.
If full turnout isn’t possible, hand walking, in-hand hill work, or even short sessions of groundwork on off days help maintain the muscle tone that keeps vertebrae properly spaced. The goal is consistent, moderate activity rather than cycles of intense work followed by days of inactivity.