Our daughter was just diagnosed with a hip problem called Legg-Perthes disease. We've been told girls have a worse case than boys. Why is that?

Legg-Calvé-Perthes disease is a bone condition named after three physicians who first described it. It is a degenerative disease of the hip joint. A loss of blood supply to the bone results in damage and degeneration of the hip.

Although boys are affected more often than girls, girls tend to have a worse prognosis. The reason for poorer outcomes in females remains unknown. There is a known delay in bone growth in this condition. But studies to analyze the bone age delay patterns show no difference between boys and girls.

Greater delays in bone growth early in the disease does predict a worse prognosis. The age of the child when the disease starts doesn't seem to affect bone age delay. The degree of bone age delay is a better predictor of severe disease. Delays of more than two years in the first stage of the disease predicts a severe case of Legg-Calvé-Perthes disease.

More studies are needed to determine the differences and cause of those differences between boys and girls.

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