Back Pain (Thoracolumbar Dysfunction)
Basic Information 
Epidemiology
Species, Age, Sex
Congenital vertebral malformations are more likely to be observed in young horses.
Genetics and Breed Predisposition
• Hyperkalemic periodic paralysis (HyPP) in Quarter Horses
• Hereditary equine regional dermal asthenia (HERDA) or hyperelastosis cutis in Quarter Horses
• Polysaccharide storage myopathy (PSSM) in Quarter Horse–related breeds, Warmbloods, and draft horses
• Breed predisposition for dorsal spinous process impingement or overriding in Thoroughbreds and lordosis in Saddlebreds
Clinical Presentation
Disease Forms/Subtypes
• Congenital: Vertebral malformations, ankylosis
• Degenerative: Osteoarthritis, spondylosis
• Acquired: Dorsal spinous process impingement
• Traumatic: Pressure sores from ill-fitting tack, spinous process or vertebral body fractures
• Infectious: Equine protozoal myeloencephalitis (EPM), equine herpesvirus type 1 (EHV-1) myeloencephalitis
• Iatrogenic: Improper or ill-fitting saddle, saddle pads, or harness
History, Chief Complaint
• Skin lesions or bumps in the saddle region
• Asymmetric sweat marks on the back or dirt patterns on the saddle pad
• Change in spinal posture or soft tissue swelling
• Resentment to grooming, saddle placement, or tightening of the girth or cinch
• History of flipping over backward
• Bucking and rearing when mounted or ridden
• Pins ears or swishes tail when mounted or ridden
• Poor performance and vague gait abnormalities
Physical Exam Findings
• Alopecia or white hairs in the region of saddle or harness
• Increased heat or palpable swelling
• Pain elicited on palpation of the thoracolumbar soft tissues or dorsal spinous processes
• Thoracic lordosis, lumbar kyphosis, or scoliosis
• Flattened and widened dorsal contour of the withers
• Dorsally prominent or laterally deviated dorsal spinous process
• Reduced active and passive range of spinal motion in lateral bending or extension
• Generalized lack of muscle development or local muscle atrophy
• Epaxial muscle hypertonicity or fasciculations
• Exaggerated cutaneous trunci reflex or spinal reflexes
• Ataxia, spasticity, or weakness (in pelvic limbs only)
• Reduced dorsoventral spinal mobility at the walk, trot, or canter
• Poor pelvic limb engagement and propulsion during the canter
