02/25/2026
Interspinous Ligament Fibrosis in Kissing Spine
What the Research Means for Rehab, Load Management, and Soft Tissue Modalities
Kissing spine is not just bone on bone. The interspinous ligament remodels under chronic load, and your training choices shape that adaptation.
Why the Interspinous Ligament Matters in Kissing Spine
Overriding dorsal spinous processes (ORSP, commonly called kissing spine) is not solely a bony spacing issue. The interspinous ligament (ISL), which spans between adjacent dorsal spinous processes, is a load bearing soft tissue structure that adapts to chronic compressive and shear forces generated by posture, training load, saddle fit, and rider biomechanics.
Key Histological Evidence
Ehrle et al., 2019, The Veterinary Journal
Histological examination of the interspinous ligament in horses with overriding spinous processes.
Key findings
• Disrupted collagen fiber alignment and altered ligament architecture in horses with ORSP compared with controls
• Increased fibrocartilaginous tissue within the interspinous ligament, consistent with chronic tissue remodeling
• Higher sensory nerve fiber density in affected ligaments, supporting the ligament as a potential pain generating structure
Clinical Relevance
These findings indicate chronic load related tissue adaptation rather than an isolated acute inflammatory event.
Clinical Context and Pain Mechanisms
Pilati et al., 2023, Animals (narrative review)
Impinging and overriding spinous processes in horses.
Key findings
• ORSP related pain is multifactorial. Bone proximity, ligamentous tissues, paraspinal muscles, and neuromuscular control all contribute to clinical presentation.
Jeffcott, 1980
Key findings
• Thoracolumbar pain in performance horses frequently reflects soft tissue dysfunction and altered movement patterns in addition to radiographic findings.
Applied takeaway
The interspinous ligament in kissing spine undergoes chronic remodeling under load. Pain and performance limitation are influenced by how the horse moves and is loaded, not solely by radiographic spacing of the spinous processes.
Mechanism: Why Fibrosis Develops in the Interspinous Ligament
Biomechanics and tissue adaptation
Sustained thoracolumbar extension patterns, limited spinal flexion capacity, and repetitive compressive loading increase focal stress between dorsal spinous processes. Over time, ligament tissue adapts via collagen reorganization and fibrocartilaginous metaplasia (Ehrle et al., 2019). These load driven adaptations are consistent with reduced tissue compliance and altered force transmission across the thoracolumbar motion segments.
Neuromuscular control
Segmental spinal control deficits and paraspinal muscle inhibition can concentrate load into specific interspinous spaces during transitions, collection, and sitting gaits. Protective muscle tone can further limit spinal motion variability, reinforcing focal stress patterns.
Load management
Rapid increases in workload, prolonged work in postures that bias extension, or tack factors that restrict thoracolumbar motion may accelerate maladaptive tissue remodeling.
What This Means for Rehab Programming
1) Training design should reduce focal interspinous compression
Progress thoracolumbar flexion capacity and controlled eccentric topline loading before increasing collection demands. Chiropractic assessment and adjustment can be used to restore segmental spinal mobility and reduce protective guarding that biases the horse into sustained extension postures. When combined with appropriately progressed training design, this supports more even load distribution across the thoracolumbar segments rather than focal interspinous compression. Avoid prolonged training blocks that bias extension early in a conditioning cycle.
2) Neuromuscular re-education is central
Low load postural control tasks that improve segmental stability and pelvic thoracolumbar coordination should precede higher intensity collected or jumping work. Chiropractic care can improve segmental spinal mobility, joint afferent input, and neuromuscular coordination, creating a more receptive system for therapeutic exercise and postural retraining. Rider asymmetries should be assessed, as unilateral loading patterns can bias stress into specific interspinous spaces. Integrating rider biomechanics work alongside equine care improves durability of neuromotor adaptations.
3) Modalities such as IASTM and chiropractic care are integral components of multimodal rehab
While equine specific randomized controlled trial data evaluating IASTM for interspinous ligament fibrosis are limited, current conservative best practice in sport horse management supports a multimodal approach that integrates soft tissue modalities, chiropractic care, and therapeutic exercise. From a mechanobiology and neurophysiology perspective, IASTM and targeted manual therapy may influence superficial and paraspinal tissue stiffness, local perfusion, and afferent input from cutaneous and myofascial mechanoreceptors. These effects can reduce protective muscle tone and improve tolerance to movement retraining, creating a more receptive neuromuscular environment for corrective exercise.
Chiropractic care can improve segmental spinal mobility, joint afferent input, and neuromuscular coordination, creating a more receptive system for therapeutic exercise. Although fibrocartilaginous remodeling within the interspinous ligament is not reversed by manual therapies alone, combining IASTM and chiropractic care with biomechanics driven load modification and neuromuscular retraining represents the most clinically effective conservative strategy currently supported by the literature and contemporary sport horse practice.
In performance horses, durable improvements in comfort and movement quality are most consistently observed when chiropractic care and IASTM are used to improve tissue and joint receptivity to load, and therapeutic exercise is used to drive lasting neuromuscular adaptation.
Contraindications, Limitations, and Common Misinterpretations
Contraindications
• Avoid forced end range thoracolumbar extension in early phase rehabilitation.
Limitations of the research
• Radiographic severity of ORSP does not reliably correlate with pain or performance impairment.
• Histologic findings do not predict individual clinical response to conservative rehabilitation.
Common misinterpretations
• ORSP is only a bone problem. Evidence indicates ligamentous and neuromuscular contributors are clinically relevant.
• Soft tissue modalities are most effective when integrated with chiropractic care and targeted therapeutic exercise as part of a multimodal, biomechanics driven rehabilitation approach. Current evidence and clinical consensus indicate that combined conservative care supports improvements in spinal mobility, neuromuscular function, and pain modulation more reliably than any single modality used in isolation.
• More topline work is always beneficial. Without appropriate spinal control, topline loading may increase focal interspinous compression.
Practical, Safe Takeaways for Riders and Trainers
Barn level application
1. Audit posture and workload
Reduce sustained thoracolumbar extension early in training cycles. Build flexion capacity and neutral spinal control before increasing collection.
2. Rebuild spinal control before intensity
Progress postural control and segmental stability before increasing sitting gaits, collected work, or jumping volume.
3. Use modalities to support movement retraining
If manual therapy or IASTM is used, pair it with immediate, corrective therapeutic exercises to reinforce improved motor patterns.
Clinical pearl for practitioners
In ORSP cases, assess rider asymmetry and habitual thoracolumbar extension bias. Small changes in rider pelvic control and symmetry can materially alter interspinous load distribution even when radiographs remain unchanged.
Evidence aligned CTA
Prioritize movement assessment and progressive load design informed by current biomechanics and histology research. Educating riders and trainers on how daily training choices shape tissue adaptation is central to durable performance management.
Primary references
Ehrle A, Ressel L, Ricci E, Merle R, Singer ER. 2019. The Veterinary Journal. Histological examination of the interspinous ligament in horses with overriding spinous processes.
Pilati N et al. 2023. Animals. Impinging and overriding spinous processes in horses: narrative review.
Jeffcott LB. 1980. Equine Veterinary Journal. Disorders of the thoracolumbar spine of the horse.
