There are two layers of laminae in the hoof. The layer next to the hoof wall has no blood or nervous tissue and is called the insensitive laminae. When the sensitive laminae becomes inflamed it creates a lot of pressure and can cause pain and instability. Major changes in normal gut bacteria produced when a horse eats too much grain, or grazes lush pasture, or when a mare has a retained placenta may cause laminitis. Illnesses like infectious diseases, colic, or a surgery may trigger the disease.
Stress seems to be a major motivator of laminitis.
Even the stress of transportation may cause laminitis. Overweight animals and especially ponies are more prone to get laminitis. Trauma to the hoof or foot may also be a cause. If the horse is worked repeatedly on hard ground or pavement, laminitis may develop. Dr. Martinelli notes that there are also cases where there is no apparent reason for the horse to have laminitis, but it is lame.