define perthes disease
Legg Perthes Disease in Dogs. Definition. Legg Perthes Disease, also known as aseptic necrosis of the femoral head, Legg-Calve-Perthes Disease, Perthes Disease or simply Leggâs Disease, is a condition that involves spontaneous disintegration and collapse of the top of a dogâs long thigh bone, the femur, which connects the knee to the hip. The cause of this disease is not known.