Progressive structural and functional change in horses: a conceptual framework for systemic equine (patho-)physiology.

Abstract

A wide range of locomotor, postural, and behavioral pathophysiology in horses-often grouped under terms such as Topline Syndrome, Myofascial Dysfunction, or Poor Posture Syndrome-lack a coherent systemic explanation. These presentations share reduced performance, stability, and resilience, yet are commonly managed through isolated symptom-focused interventions. To address this gap, we propose progressive structural and functional change (PSF) as a systemic framework describing progressive reorganization processes within the equine body that link fragmented pathological domains into a coherent pattern of structural and functional (dys-)regulation. PSF comprises two trajectories: progressive structural and functional loss (PSF), driven by a maladaptive self-amplifying reorganization of motion patterns, and progressive structural and functional gain (PSF), a self-stabilizing pattern of physiological recovery and improving functional organization. We identify functional inversion as central mechanism driving PSF. It denotes a systemic reversal of physiological force directions and load-transfer roles, characterized by a persistently open lumbosacral joint, a shift in stance-phase timing, and reciprocal remodeling of fore- and hind hoof morphology. These interdependent changes are interpreted as creating conditions consistent with a broad spectrum of secondary symptoms and pathologies. This Hypothesis and Theory article presents a concept-driven framework derived from applied field observations in horse training and rehabilitation, rather than from institutionally based academic research in equine science. It is based on long-term exploratory field observations and includes ten retrospectively documented case studies of horses followed over several years. The heterogeneous cases (varying breed, age, training background) serve as illustrative examples of recurring functional patterns rather than as controlled sample. Our observations suggest that restoring physiological lumbosacral function, facilitating horse-initiated horizontal tension toward the bit, and managing hoof morphology can support the system shift toward PSF, while unresolved local pathologies limit systemic reorganization. The PSF framework integrates unconnected clinical findings into a conceptually defined systemic process, identifies measurable screening targets, and may support practitioners in prioritizing rehabilitation strategies. It generates falsifiable predictions that can be examined at two levels-through low-threshold, practice-based observational criteria and through advanced biomechanical measurement approaches-thereby enabling both practice-based application by horse owners and scientific validation. The framework aims to complement welfare-oriented veterinary prevention, diagnostics, and rehabilitation.