Morphological classification of radiographic insertional enthesopathies of the nuchal ligament in asymptomatic show jumping horses

Radiographic insertional enthesopathy of the nuchal ligament in sport horses remains a poorly characterized orthopedic phenomenon, with limited and inconsistent terminology in the scientific literature. This prospective, cross-sectional observational study investigated the prevalence, morphology, and localization of nuchal ligament enthesopathies in a cohort of 35 show jumping horses. The inclusion criteria required horses to be actively competing at 1.0–1.5 m levels without current clinical signs of cervical pain. This prospective, cross- sectional observational study investigated the prevalence, morphology, and localization of nuchal ligament enthesopathies in a cohort of 35 actively competing horses using clinical and radiological assessments. Following a standardized clinical examination of the occipital region, which revealed no abnormalities, radiological evaluations were performed. In the radiographic assessment, the criteria for identifying insertional enthesopathies were defined as the presence of new bone formations at the caudal aspect of the occipital squama. Based on these criteria, such morphological changes were detected in 91% ( n = 32) of the evaluated individuals. Two principal morphological types were discerned: rounded and coronoid-like bone formations, with comparable distribution in age groups. Enthesophyte localization most encompassed both the upper and lower regions of the occipital plate but was rarely confined to ligament insertion alone. No correlation was found between enthesophyte size, shape, or location and sex or breed. However, horses over 7 years of age demonstrated significantly greater length, depth, sum of their length and depth, and surface area of the new bone formations. Furthermore, older horses more frequently displayed enthesophytes in both the upper and lower positions compared to the upper position alone. Given their high prevalence in actively competing, asymptomatic horses, these progressive morphological changes likely represent an adaptive remodeling process, making their primary clinical significance less likely in this population. Nevertheless, long-term follow-up and further biomechanical investigations are warranted to definitively rule out any delayed effects on equine performance.