Equine Navicular Syndrome: Historical, Pathological and Biomechanical Insights into Pathogenesis and Treatment

Abstract

Because horses were critical for transportation and the military, equine diseases have been studied for centuries. Navicular syndrome (NS), a common cause of lameness in modern horses, was definitively described in 1816 and rapidly increased in incidence. Historical records indicate this time frame coincides with the development of macadam pavement. NS was immediately recognized as a disease of ‘work’, yet most studies have exclusively focused on the lesions in the foot. For this study the pathology of NS was reviewed and found to be consistent with compression–induced injury, which implicates overloading by aberrant biomechanical forces as a potential cause. Assessment of 4 cases of clinical NS revealed all had significant transversal rotation of the vertebral column, associated with the metacarpal bone passing the vertical before the commencement of the propulsive stage of the stride, a kinematic that was confirmed to compress the navicular structures on dissected specimens. Correction of these biomechanical abnormalities through targeted training exercises restored soundness and resulted in all horses returning to work and remaining sound. Incorporation of historical and biomechanical insights with the pathology of equine degenerative joint diseases can provide the broad perspective needed both understand and treat these devastating conditions.