08/27/2025
So here’s our lameness case from the other day. This was a hard one! Sometimes even I learn something new after all of these years 🧐 I did side by side comparisons with the normal imaging on top and our patient views on the bottom. If you look at the navicular bone closely you can see the fractures present. This is not a common place to have a fracture and this horse is only 4 years old. He is ridden in the pasture and does not have shoes on, but after a little research it appears he most likely has a tripartite navicular bone.
A bipartite or tripartite navicular bone in a horse is a congenital condition where the bone fails to fully fuse during fetal development, appearing in radiographs as two or more separate pieces with smooth, symmetrical edges. Unlike a fracture, this anomaly is typically present from birth and can occur on one or both forelimbs. While some horses remain sound, others experience chronic heel pain, stumbles, and a toe-first landing, mimicking the signs of navicular disease.
Causes and Appearance
Congenital Origin: The condition arises from the two halves of the navicular bone ossifying (forming bone) separately and failing to join during development.
Radiographic Characteristics: Radiographs will show one or two lucent lines or wide radiolucent regions between the bone pieces, with smooth and symmetrical edges.
Bilateral Nature: It is often seen in both forelimbs.
Symptoms
Chronic Heel Pain: Horses may exhibit pain in their heels.
Lameness: A mild, progressive lameness is common.
Gait Abnormalities: Symptoms can include a shortened stride, head bobbing, and landing the hoof "toe-first".
Stumbling: The horse may be more prone to stumbling.
Diagnosis and Management
A veterinarian will identify a bipartite navicular bone through radiographs.
Distinguishing from Fracture:
It is crucial to differentiate a bipartite navicular bone from a navicular bone fracture, as they have different prognoses and treatments.
Addressing Lameness:
If the horse is lame, the approach to managing the symptoms will be similar to that for other causes of navicular disease, potentially including corrective shoeing and medications to reduce inflammation.
In this case, since we got the information we were looking for in these films we did not radiograph the opposite limb. . While often asymptomatic, the stress on the partition site can lead to chronic heel pain and degenerative changes over time, resulting in lameness. Because this was not an incidental finding and was accompanied by lameness the prognosis for return to function is poor.