Founder and laminitis are closely related but describe different aspects of the same disease process. Laminitis is the inflammation of the laminae—the sensitive tissue layers inside the hoof that attach the hoof wall to the coffin bone. Founder occurs when laminitis is severe enough to cause the coffin bone to rotate or sink within the hoof capsule, representing the structural damage that results from prolonged or acute laminitis. In other words, all cases of founder involve laminitis, but not all laminitis cases progress to founder.
Laminitis develops from various triggers including grain overload, rich pasture grazing, infection, metabolic disorders like insulin resistance, or trauma. The inflammation causes pain, heat in the hooves, reluctance to move, and a characteristic "parking out" stance where the horse stretches its front legs forward to relieve pressure on the affected hooves. If caught early and treated aggressively, laminitis may resolve without permanent damage.
Founder represents the chronic or severe form, where the laminae have been damaged so extensively that the coffin bone loses support and shifts position. Once founder occurs, permanent structural changes have happened. The horse may have lasting lameness, a distinctive "founder rings" pattern on the hoof wall, and a concave sole. Chronic founder can make a horse unusable for riding, though management with specialized farrier work and pain relief may maintain quality of life.
Treatment differs by stage: acute laminitis requires immediate veterinary care to control inflammation and prevent progression to founder, while chronic founder focuses on managing pain and providing supportive farrier care to the compromised hoof structure.