Kissing Spine in Horses: What It Is, How It's Diagnosed, and Treatment Options

Your horse is cinchy. Drops away from the mounting block. Bucks into the canter transition. Won't round through the back. You've tried a new saddle, a chiropractor, massage, a different bit. Nothing sticks. Then someone mentions kissing spine, and suddenly you're down a rabbit hole of radiographs, conflicting opinions, and decisions about surgery. Sound familiar? You're not alone. Kissing spine has become one of the most discussed and most misunderstood conditions in equine practice, partly because the diagnosis isn't always as straightforward as the X-rays make it appear.

Anatomy of the Dorsal Spinous Processes

Every vertebra in the horse's spine has a dorsal spinous process: a bony projection that extends upward from the vertebral body. If you run your hand along a horse's topline, the tips of these processes are what you feel beneath the muscle and connective tissue. They serve as attachment points for the powerful muscles and ligaments that support and move the back.

The thoracic vertebrae have the tallest spinous processes, and they're tallest in the withers region (approximately T3-T7). As you move caudally toward the saddle area (T10-T18), the processes become shorter and the spaces between them narrow. This is precisely where kissing spine most frequently develops.

In a normal spine, gaps of varying width separate adjacent spinous processes. Interspinous ligaments span these gaps, providing both connection and cushioning. The supraspinous ligament runs along the dorsal tips, binding everything together in a continuous chain. This architecture allows the back to flex, extend, and laterally bend within a controlled range.

The equine skeletal system didn't evolve to carry a rider. That's the uncomfortable truth underlying a lot of back pathology. The horse's spine functions beautifully as a suspension bridge connecting forelimb and hindlimb, with the thoracolumbar region acting as the main span. Adding a rider's weight, especially one who sits heavily or bounces, concentrates force in exactly the region where spinous processes are most crowded together.

What Happens in Kissing Spine

Overriding dorsal spinous processes (ORDSP) occur when adjacent spinous processes lose the normal gap between them and make contact. In advanced cases, they overlap, remodel, and develop sclerosis (increased bone density) at the points of contact. The interspinous ligament between affected vertebrae may become inflamed, torn, or fibrotic.

The impingement creates pain through several mechanisms. Bone-on-bone contact generates periosteal inflammation. The periosteum (outer bone covering) is densely innervated, so even modest pressure produces significant discomfort. Interspinous ligament damage adds another pain source. Secondary muscle spasm in the epaxial muscles (longissimus dorsi, multifidus) develops as the horse guards the area, creating a cycle of pain, tension, and abnormal movement that feeds itself.

Most commonly affected region: T13-T18, which corresponds directly to where the saddle sits and where the rider's weight concentrates. The anticlinal vertebra (T16 in most horses, where the spinous processes shift from caudal to cranial angulation) is a frequent epicenter. T10-T13 involvement is also common. Lumbar kissing spine occurs but less frequently.

The Incidental Finding Problem

Here's what makes kissing spine genuinely tricky: radiographic changes don't reliably predict clinical pain. Multiple studies have demonstrated that a significant percentage of clinically sound, normally performing horses have radiographic evidence of spinous process impingement. One widely cited study found overriding or close spinous processes in nearly 86% of Thoroughbreds examined, most with no clinical signs whatsoever.

This means that taking radiographs and finding kissing spine does not automatically explain your horse's back pain. It might. But it might be a coincidental finding alongside a different primary issue: poor saddle fit, sacroiliac dysfunction, hindlimb lameness referring pain to the back, or primary muscle pathology.

The clinical significance of radiographic changes depends on several factors:

• Correlation with clinical signs: Does the horse show pain specifically in the region where radiographic changes are present?
• Response to diagnostic analgesia: Does local anesthetic injected between the affected spinous processes eliminate or significantly reduce pain behaviors? This is the most important diagnostic step
• Severity of changes: Active bone remodeling, sclerosis, and interspinous ligament mineralization carry more significance than simple narrowing of interspinous spaces
• Exclusion of other causes: A thorough lameness evaluation should rule out or identify concurrent issues

A responsible workup doesn't stop at radiographs. It includes a complete physical examination, ridden evaluation when possible, palpation, and diagnostic local analgesia. Nuclear scintigraphy (bone scan) can identify areas of active bone remodeling versus chronic, stable changes, adding another layer of diagnostic information.

Clinical Signs: More Than Just "Back Pain"

Horses with clinically significant kissing spine can present in wildly different ways depending on severity, exact location, and the individual horse's temperament. Some scream about it. Others quietly compensate until the problem becomes severe.

Common presentations include:

• Strong reaction to palpation along the dorsal midline, especially in the saddle region
• Cold-backed behavior: humping, bucking, or stiffness when first mounted that improves with work
• Difficulty engaging the hindquarters and working "over the back"
• Resistance to lateral bending
• Bucking or crow-hopping during transitions, particularly walk-to-canter
• Reluctance to jump or loss of jumping form
• Behavioral changes: girthiness, ears pinned during grooming, avoidance of being caught
• Poor performance that defies other explanations
• Muscle atrophy along the topline despite adequate work and nutrition

The connection between saddle fit and kissing spine runs in both directions. A poorly fitted saddle can create focal pressure that contributes to spinous process impingement. Conversely, a horse with kissing spine may struggle with any saddle because the underlying bony pathology produces pain regardless of pressure distribution. Addressing saddle fit is always part of the management plan, but it's rarely the complete solution when true impingement exists.

Conservative Treatment Options

Corticosteroid Injection

Injecting corticosteroids directly into the interspinous spaces is one of the most common first-line treatments. Performed under ultrasound guidance (or with radiographic confirmation of needle placement), these injections deliver potent anti-inflammatory medication exactly where it's needed.

Response rates vary in published literature, with approximately 40-70% of horses showing improvement. Duration of effect is unpredictable: some horses remain comfortable for months or even a year or longer, while others relapse within weeks. Repeated injections are common. The procedure itself is relatively low-risk, quick, and can be performed in the field.

Corticosteroid injection also functions as a diagnostic tool. If the horse improves significantly after injection at specific interspinous sites, it strongly confirms those sites as clinically relevant pain generators.

Mesotherapy

Mesotherapy involves multiple small injections of a medication cocktail (typically a combination of anti-inflammatory, local anesthetic, and sometimes a muscle relaxant) into the intradermal and subcutaneous tissues along the back. The theory is that it interrupts the pain-spasm-pain cycle by acting on local nerve pathways.

Results are mixed in the literature, and the evidence base is thinner than for other treatments. However, many clinicians report good clinical results, particularly when combined with rehabilitation exercises. It tends to work best as part of a multimodal approach rather than as a standalone therapy. Treatment is usually repeated in a series of 2-3 sessions spaced weeks apart.

Shockwave Therapy

Extracorporeal shockwave therapy applied over the affected dorsal spinous processes has analgesic and potential tissue-remodeling effects. It's typically administered in 3-5 sessions at 2-3 week intervals. Some horses show meaningful improvement. Like mesotherapy, it's generally used as part of a broader treatment plan.

Surgical Options

Interspinous Ligament Desmotomy (ISLD)

ISLD has become the most popular surgical intervention for kissing spine, largely because it can be performed standing under sedation. The procedure involves cutting the interspinous ligament between affected spinous processes. This releases tension, allows the processes to separate slightly, and eliminates the ligament as a pain source.

Published outcomes are encouraging. A landmark study from Cornell reported that approximately 72% of horses treated with ISLD returned to their previous level of work or higher. The surgery is minimally invasive compared to older approaches, recovery is relatively straightforward, and complication rates are low.

Post-surgical rehabilitation is critical to success. Without targeted exercise to rebuild the epaxial musculature, the biomechanical problems that contributed to kissing spine persist. Horses that undergo ISLD and then sit in a field for months without structured rehab tend to have poorer outcomes than those following a progressive exercise program.

Subtotal Ostectomy

For severe cases or those that don't respond to ISLD, partial removal of the dorsal spinous processes (subtotal ostectomy) removes the impinging bone directly. This can be performed standing or under general anesthesia depending on the extent and location. It's a more aggressive procedure with longer recovery times but addresses the mechanical problem definitively.

Rehabilitation: The Non-Negotiable Component

Regardless of whether treatment is conservative or surgical, rehabilitation determines long-term success. The goal is strengthening the multifidus and longissimus muscles that stabilize and support the thoracolumbar spine, while encouraging the horse to work in a biomechanically correct posture.

Effective rehabilitation strategies include:

• Dynamic mobilization exercises ("carrot stretches"): Encouraging the horse to flex, extend, and laterally bend the spine through treat-guided movements. These exercises activate the multifidus and improve intersegmental stability. Research by Dr. Hilary Clayton has documented measurable increases in multifidus cross-sectional area with consistent performance of these exercises
• Ground poles and cavaletti: Walking and trotting over ground poles encourages the horse to engage core muscles and actively lift the back
• Hill work: Walking up and down inclines builds hindquarter and back strength without high concussive impact
• Lunging with proper technique: Encouraging the horse to reach into a low, round frame on a large circle promotes back engagement. Tight circles or hollow frames do the opposite
• Gradual return to ridden work: Typically beginning 6-8 weeks post-surgery, with focus on long and low frames before asking for collection

A realistic timeline for full rehabilitation after ISLD or ostectomy is 4-6 months. Rushing the process risks relapse. Patience pays dividends here.

To see exactly how the dorsal spinous processes relate to the surrounding musculature and the vertebral bodies themselves, explore our interactive 3D spine models. The spatial relationships become much clearer when you can rotate and zoom through the structures.

Frequently Asked Questions

Sources

• Cornell University College of Veterinary Medicine - ISLD Outcomes Research
• Michigan State University Veterinary Medical Center - Equine Back Pain Diagnostics
• Journal of Equine Veterinary Science - Overriding Dorsal Spinous Processes Studies
• Dr. Hilary Clayton, Sport Horse Science - Dynamic Mobilization Exercise Research