Clinical signs of laminitis include tender feet that develop into inability to walk, an increased digital pulse, and elevated temperature in the hooves. Severe cases with outwardly visible clinical signs and disease progression can lead to perforation of the coffin bone by the hoof sole and the inability to stand, possibly requiring euthanasia.
Laminitis literally means inflammation of the laminae, the cells that connect the coffin bone to the hoof wall, and while it remains controversial whether this is the primary mechanism of disease, signs of inflammation appear very early in some cases of the disease. Severe inflammation is believed to damage the laminae, resulting in a reduction in adhesion. The normal forces exerted on the hoof are then strong enough to tear the remaining laminae, resulting in a rupture of the connection between coffin bone and hoof wall. When severe enough, it results in displacement of the coffin bone in the hoof capsule, which in the worst case can lead to breaching of the sole. Most cases of laminitis occur in both front feet, but laminitis also occurs in all four feet, just the hind feet, or one foot.
One of the newest theories for the molecular basis of laminitis involves matrix metalloproteinases (MMPs). Metalloproteinases are enzymes that can degrade collagen, growth factors and cytokines to remodel the extracellular matrix of tissues. To prevent tissue damage, they are regulated by tissue inhibitors of metalloproteinases (TIMPs). In the case of laminitis, an underlying cause is thought to be an imbalance of MMPs and TIMPs, favoring MMPs so that they can cleave substances in the extracellular matrix and thereby degrade the basement membrane.
In-house veterinary research has shown marked improvement in a number of cases with oral administration of collagen peptides to laminitis horses.