Understand what Laminitis is. Laminitis is a disease that causes lameness in horses. It was once associated primarily with overweight ponies, but it can affect any age or size of horse. With this disease, the laminae weaken, which attach the pedal bone to the inside of the hoof. The horses pedal bone detaches from the inside of the hoof. Therefore, the pedal bone can turn, and sometimes, it even pushes through the sole. When it pushes through the sole, it's called founder..