NEW YORK - The painful hoof disease affecting Barbaro is no stranger to horse racing fans: Secretariat, the 1973 Triple Crown winner, was euthanized because of it in 1989.

The disease, called laminitis or founder, involves inflammation and structural damage to tissue that bonds the horse’s bone to the inner wall of the hoof. In severe cases, this connection can be so damaged that a horse literally can walk out of its foot, said Rob Sigafoos, a horse expert at the University of Pennsylvania.

Laminitis has multiple causes, and scientists still are debating exactly what prompts the disease, he said. In Barbaro’s case, it’s blamed on the uneven weight distribution between the rear legs after the injury to the right hind leg in the Preakness.

“There’s no book you go to that says here’s laminitis 101 ... put tab A in slot B. It’s not that simple,” said Dean Richardson, the chief surgeon who has been treating Barbaro since the colt suffered catastrophic injuries. “It’s a devastating problem in horses that nobody has a solution to.”

The disease also is seen in horses with systemic infections and mares that retain the placenta. Diet also has been implicated. When the condition strikes their front feet, horses can be seen trying to shift their weight to their back feet.

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Laminitis is treatable with drugs and special horse shoes, especially in mild cases. A 2000 report by the federal government, “Lameness and Laminitis in U.S. Horses,” found laminitis was reported in about 2 percent of horses during a year-long period. That included new and existing cases. The 28-state survey covered U.S. horse operations with at least three animals.