Kissing spine is a condition where the bony projections on top of a horse’s vertebrae sit too close together, eventually touching or overlapping instead of maintaining healthy spacing. Formally called overriding dorsal spinous processes (ORDSP), it’s one of the most common causes of back pain in horses and a frequent explanation for unexplained behavioral or performance problems under saddle.
What Happens in the Spine
Each vertebra in a horse’s back has a tall, fin-like projection called a dorsal spinous process that rises upward from the spine. In a healthy back, these projections are evenly spaced with soft tissue and ligament filling the gaps between them. In a horse with kissing spine, two or more of these projections crowd together until they make contact. The repeated bone-on-bone friction causes inflammation, pain, and progressive damage to the bone surfaces.
The condition most often develops in the thoracolumbar region, roughly the area under and just behind the saddle. This is where the spinous processes are tallest and most closely spaced even in a normal horse, making it the area most vulnerable to crowding. It’s worth noting that the position of these vertebrae shifts with the horse’s posture and neck position, which means the degree of impingement can change depending on how the horse carries itself.
Signs to Watch For
Kissing spine rarely shows up as obvious lameness. Instead, most horses express their discomfort through behavior changes and performance issues that owners sometimes mistake for training problems or attitude. Common signs include sensitivity or flinching when the back is groomed or palpated, girthiness (pinning ears or moving away when the girth is tightened), reluctance to bend or collect, a shortened stride, difficulty picking up the correct lead, and resistance to transitions. Some horses buck, rear, or refuse jumps. Others simply become progressively dull and unwilling under saddle.
Because back pain can refer to other areas and mimic other conditions, it often takes time for owners to connect the dots. A horse that suddenly starts acting “cold-backed” when saddled, hollowing its back under the rider, or losing muscle along the topline deserves a closer look. The behavioral signs tend to worsen as the condition progresses and more bone damage accumulates.
How Kissing Spine Is Diagnosed
X-rays are the primary tool for identifying kissing spine. Standing radiographs of the back can reveal narrowed spaces between spinous processes, areas where processes touch or overlap, and changes to the bone itself. Veterinarians grade the severity on a four-point scale:
- Grade 1: Narrowing of the space between spinous processes
- Grade 2: Hardening (sclerosis) along the bone margins where processes are crowding
- Grade 3: Bone loss (lysis) developing at the contact points
- Grade 4: Severe remodeling of the bone
One important complication in diagnosis: many horses show radiographic evidence of kissing spine without any clinical signs of pain. This means X-rays alone don’t tell the full story. A veterinarian typically combines imaging with a physical exam, palpation of the back, and sometimes diagnostic nerve blocks (injecting local anesthetic between the affected processes to see if the horse’s pain resolves) to confirm that the radiographic findings actually match the clinical problem.
Additional imaging tools can help in ambiguous cases. Thermography uses an infrared camera to detect heat patterns along the back that suggest inflammation. Bone scans (nuclear scintigraphy) highlight areas of active bone remodeling, which can distinguish between old, stable changes and processes that are currently causing pain. Ultrasound can assess the soft tissues and ligaments between the spinous processes.
What Causes It
There’s no single cause. Conformation plays a significant role: horses with short backs naturally have less space between spinous processes and are more vulnerable to crowding. Thoroughbreds and warmbloods appear overrepresented in clinical studies, though the condition has been identified across breeds.
Poor posture and weak core muscles can contribute. A horse that habitually travels with a hollow, dropped back brings the spinous processes closer together, while a horse that lifts through its core and rounds its back creates more space. This is why saddle fit, training methods, and rider balance all factor into the equation. A poorly fitting saddle that causes a horse to brace and hollow its back can accelerate the problem, and a heavy or unbalanced rider adds further load to an already vulnerable area. Some horses also develop kissing spine after an injury leads to compensatory movement patterns that load the back abnormally over time.
Non-Surgical Treatment
For mild to moderate cases, treatment typically starts with a combination of pain management and targeted rehabilitation. Corticosteroid injections between the affected spinous processes can reduce inflammation and provide pain relief, sometimes for weeks to months. Shockwave therapy is another option that aims to reduce pain and stimulate healing in the affected area. Anti-inflammatory medications can help manage discomfort during rehabilitation.
The real backbone of conservative treatment, though, is changing how the horse uses its body. The goal is to strengthen the muscles that support and lift the back, particularly the deep core muscles along the underside of the spine. Exercises that encourage the horse to lower its head and round its back help open up the spaces between the spinous processes. Carrot stretches (using a treat to guide the horse into lateral and downward stretches), belly lifts (applying gentle pressure under the belly to encourage the horse to engage its core and lift the back), and groundwork with training aids that promote a rounded frame are all commonly used. Lunging on a circle with a focus on correct posture rather than speed is often part of the program.
Saddle fit should be evaluated carefully. A saddle that bridges across the back or creates pressure points over the affected area will undermine any treatment progress.
Surgical Options and Outcomes
When conservative management doesn’t provide enough relief, two surgical approaches are most common.
Interspinous Ligament Desmotomy
This procedure involves cutting the ligament between the affected spinous processes. By releasing the tension, it allows the processes to spread apart slightly and reduces the bone-on-bone contact. It’s a relatively minimally invasive procedure, and horses typically return to a controlled exercise plan and begin work again within 3 to 6 weeks. A study of 71 horses treated with this approach found that 91% returned to some level of performance, with about 53% reaching their previous performance level or higher.
Bone Removal (Subtotal Ostectomy)
In more severe cases, the surgeon removes portions of the crowded spinous processes to create permanent space between them. This is a more involved surgery with a longer recovery. Horses generally return to light work within 3 to 6 months. A large study of 215 horses treated this way found that 81% returned to athletic use, with 72% returning to full work.
Both surgeries have good success rates, but they work best when paired with a rehabilitation program that builds the core strength needed to support the back long term. Surgery addresses the structural problem, but without the muscular support to maintain correct posture, the remaining or adjacent spinous processes can still become problematic.
Long-Term Management
Kissing spine is a condition that benefits from ongoing attention rather than a one-time fix. Even after successful treatment or surgery, maintaining core strength and correct movement patterns is essential. Regular turnout helps because horses that move freely tend to use their backs more naturally than those standing in stalls for long periods. A consistent exercise program that emphasizes correct posture, appropriate warm-up and cool-down routines, and regular saddle fit checks all contribute to keeping a horse comfortable.
Many horses with kissing spine go on to have full athletic careers once the condition is properly managed. The key is recognizing the signs early, getting an accurate diagnosis that correlates imaging with clinical symptoms, and committing to the rehabilitation work that addresses the root cause rather than just the pain.