One of the most common ailments which can change this picture rapidly is laminitis. The disease may be acute or chronic and may affect one or all four feet at any one time. The forefeet are affected more frequently. There are many factors that can cause laminitis. Accidental overfeeding, such as a horse breaking into a grain sack, also may result in an attack of founder.
Ponies appear to be more susceptible to laminitis than horses.
Also, horses between the ages of four and ten years appear to be more susceptible than other horses. Acute laminitis has a sudden onset. Horses apparently normal in their movement one night may be in severe pain and reluctant to move the following morning. The animal may be standing with all four feet close together, if all four feet are affected, with its head low and its back arched. If only the front feet are affected, the horse will shift the hind legs underneath it to try to put most of its weight on the back feet and vice versa.