Pathological changes in the navicular bone and associated structures of the horse.
Authors: Doige, Hoffer
Journal: Canadian journal of comparative medicine : Revue canadienne de medecine comparee
Summary
# Editorial Summary: Pathological Changes in the Navicular Bone and Associated Structures Navicular disease remains a common cause of chronic lameness in horses, yet distinguishing clinically significant pathology from age-related degenerative change has proven challenging. Doige and Hoffer examined navicular bones from 74 horses at necropsy (aged 8 months to 30 years), with eight animals having a documented clinical history of navicular disease, to characterise the structural changes associated with the condition. Fibrocartilaginous degeneration on both the navicular bone surface and deep flexor tendon proved to be age-dependent findings in sound horses; however, clinically affected animals displayed more extensive lesions accompanied by adhesions and subchondral cavitation—distinguishing features that may correlate with lameness. Notably, osteophytes were uncommon in diseased horses despite being present in 12 animals overall, suggesting they represent a different pathological pathway, whilst nutrient foramina morphology differed significantly in affected horses, with characteristically small external openings that enlarged internally. These findings challenge traditional assumptions about navicular pathology, as vascular occlusion was identified in both sound and lame horses without evidence of thrombosis or ischaemic necrosis, indicating that secondary vascular disease may not be the primary driver of clinical signs—a distinction with important implications for how practitioners interpret imaging findings and counsel clients on prognosis and management strategies.
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Practical Takeaways
- •Degenerative changes visible on imaging or necropsy do not confirm navicular disease as a cause of lameness—clinical correlation is essential, as many sound horses have similar lesions
- •The presence of adhesions and subchondral cavitation appears more specific to clinical navicular disease than simple degenerative changes or osteophyte formation
- •Vascular insufficiency as previously theorized does not appear to be a primary driver of navicular disease pathology based on absence of thrombosis and ischemic necrosis
Key Findings
- •Degenerative lesions of navicular bone fibrocartilage and deep flexor tendon surfaces are age-related changes not necessarily associated with lameness (74 horses examined)
- •Horses with clinical navicular disease showed more extensive lesions with adhesions and subchondral cavitation compared to asymptomatic horses
- •Osteophytes were present in 12/74 horses (16%) and were age-related but uncommon in horses with navicular disease history
- •Occlusive vascular disease (arteriosclerosis) was found in both sound and lame horses; thrombosis and ischemic necrosis of bone were not identified in any case