It must be spring if talk about horses turns to founder. To some, founder is a serious disease, to others a temporary nuisance when their horse seems a little "foot-sore" for a week or two. Most know that horses on those early, fast-growing pastures seem to get founder in spring more than any other time of year. But does anyone really know what it is?

Laminae form the latticework that connects the inside of the hoof wall to the surface of the bone. Laminae on the inside surface of the hoof wall interlock with laminae covering the bone, and where they meet creates a connection similar to Velcro. The connection is strong, has many blood vessels running through it, and is responsible for supporting the weight of the horse. The health of the foot depends on the health of the laminae, and when laminitis occurs, the horse is in serious trouble.

If the swelling is minimal, the laminae may recover without much damage. As the swelling increases, a cascade of complications may result. First, the swelling creates pressure inside the foot that diminishes blood flow. Without enough blood, the laminae begin to die. Dead laminae don't bind together and the wall actually separates from the bone. In some this separation can be seen on the underside of the foot where the sole and wall meet (the area known as the white line).

Separation of the foot is bad enough; in some cases this separation may not be complete and only separates in patches around the foot. But any kind of separation can create a rotation of the coffin bone inside the foot because the supporting laminae aren't supporting the bone in place anymore. The tension from the muscles in the leg, normally counteracted by the strong connection of the laminae, is now strong enough to pull the back of the bone up towards the leg, thus causing the toe of the bone to point downward. This rotation of the bone can be so severe that the bone could penetrate the sole of the horse's foot. Even if the horse recovers, too much rotation and the animal won't ever be sound again.

Inflammation of the laminae could lead to separation, causing rotation of the bone. Or the separation could be so severe that the entire bone actually drops away from the hoof wall. This occurrence, often termed a "sinker," is a precursor of the complete sloughing of the foot. At this point, the horse has little to no hope of survival. Deaths in these cases usually result from infections to the exposed laminae. Because of the progression of laminitis, it should be considered a genuine threat to the horse's life. If the condition is caught in time, there is hope that the progression can be stopped and the horse saved. Catching it in time means knowing what to look for.