Navicular Disease – What is new

This schematic image of the horse’s foot shows some, but not all of the important structures within the foot. (Photo courtesy of the Horse Forum)

By Lauren Lamb, DVM

Navicular ‘disease’ is a condition that affects the navicular bone, navicular bursa, deep digital flexor tendon and/or the associated ligaments attached to the navicular bone. Navicular disease, navicular syndrome, caudal heel pain syndrome in the horse or insert some other name are all terms used to describe the same condition, pain in the heel region of a horse. For the purposes of this article, navicular disease will be the term used to describe pain from the heel region of a horse. Navicular region will refer to the navicular bone, associated ligaments, navicular bursa and deep digital flexor tendon.

Before we can talk about navicular disease, we need to step back and review the normal anatomy. The navicular bone is located behind the coffin joint, within the hoof capsule. The navicular bone articulates (forms a joint) with the coffin bone and short pastern bone, which are located on the front side of the navicular bone.

The deep digital flexor tendon runs on the back side of the navicular bone. The navicular bursa lies between the navicular bone and the deep digital flexor tendon. The bursa is a fluid filled sac that functions as a shock absorber and a lubricant for the deep digital flexor as it passes around the navicular bone. Several other small ligaments help hold the navicular bone in place. These small ligaments are extremely important and frequently contribute to the horse’s pain.

The exact cause of navicular disease is unknown. Several potential causes for the disease have been proposed.

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This radiograph shows an enlarged vascular channels in the distal aspect of the navicular bone (lollipops). This radiographic change is seen with navicular disease. (Photo courtesy of the University of Pennsylvania)