Legg-Perthes also called Legg-Calve-Perthes (LCP) disease, is a disease of the hip joints of small breeds of dogs. The head of the femur (the ball part of the ball and socket) begins to die and disintegrate. This causes limping, pain, and eventually arthritis. It usually appears between 6-12 months of age. It is treated surgically by removing the head of the femur and letting the muscles form a "false joint." It really does work.
Veterinarians have begun to address the heritability of this disease, and it is generally agreed that although in very rare cases, the disease may be brought on by trauma, it is probably genetic. It has been well documented in terriers (Border Terrier, Lakeland Terrier, Jack Russell Terriers, Wheaten Terrier), and has been proven to be hereditary in some breeds such as the Wheaten Terrier. Bilateral cases (both hind legs affected) are not considered to be the result of trauma, and are accepted to be hereditary.
(Source: Dr. John T. Payne, DVM (Diplomate, American College of Veterinary Surgeons, College of Vet Med, University of Missouri at Columbia).
LCP disease was first documented in humans and later in dogs.