Laminitis: Part 1 – Causes, clinical signs and how to diagnose laminitis

The anatomy of the foot includes the hoof wall, non-sensitive lamina, sensitive lamina and the coffin bone. (Photo courtesy of Founder Warrior)

By Lauren Lamb, DVM 

Laminitis is a common disease seen in horses of all ages. It is a severe, debilitating and painful disease that affects the horse’s feet. Laminitis is commonly seen in the front feet, but can be seen in the back feet or in worst cases scenarios all four feet. Before we get too far in our discussion of laminitis, let’s go back and review the anatomy of the horse’s foot and how this anatomy is related to laminitis. Lamina are tiny (millimeters in thickness) finger-like projections that attach the coffin bone to the hoof wall. There are two sets of lamina.

The sensitive lamina are attached to the coffin bone and extend out to the hoof wall. The non-sensitive lamina are attached to the inside of the hoof wall and extend out to the coffin bone. The sensitive and non-sensitive lamina interdigitate with each other, attaching the hoof wall to the coffin bone. This attachment supports the horse’s weight. The sensitive lamina can have a significant amount of blood flow but no blood flow in the non-sensitive lamina.

Another anatomical structure that needs to be discussed is the deep digital flexor tendon. The deep digital flexor tendon attaches to the back/bottom of the coffin bone and is responsible for flexion of the coffin, pastern, fetlock and knee joints. The deep digital flexor tendon pulls on the back of the coffin bone and places pressure on the lamina on the front of the foot. Normal healthy lamina resist the pressure placed on them by the deep digital flexor tendon.

The term laminitis literally means inflammation of the lamina. The sensitive lamina can become severely inflamed. The cause of this inflammation can be secondary to several different factors, which we will discuss later. The inflammation will weaken or kill the sensitive and non-sensitive lamina, which can result in the coffin bone rotating or sinking in the hoof capsule.

To read more pick up a copy of the December 2017 NTFR issue.