Navicular Disease and MRI

A 10-year study in the United Kingdom investigated the relationships between clinical signs, response to nerve blocks, X-ray and magnetic resonance imaging (MRI) findings for horses diagnosed with navicular disease. The 4,618 horses examined were presented with a complaint of forelimb lameness and received a typical clinical workup prior to MRI.

A diagnosis of front foot pain was made for 702 of the horses. Most (299) had a problem unrelated to the navicular apparatus, while 180 had lesions of the distal sesamoidean collateral or impar ligaments, 69 had a primary lesion of the deep digital flexor tendon (DDFT), 62 had a primary lesion of the navicular bone and 92 had some other lesion of the navicular apparatus along with navicular bone lesions.

While nerve blocks helped localize the lameness, there was no association with results of the nerve blocks and the specific lesions identified by MRI. Similarly, clinical signs and grading of the X-rays did not correctly identify lesions identified by MRI including those of the navicular bone.

Conformational abnormalities weren’t strongly associated with any particular navicular problem. However, 25% of the horses with primary navicular bone problems had a long-toe, low-heel hoof conformation. All horses were lamer when trotted in a circle compared to a straight line, usually lamer with the affected limb on the inside and usually lamer on a harder surface. Horses with primary navicular bone pathology were lamer when the affected limb was on the outside of the circle and had higher…