The term "osteochondritis" appears defective, for it seems to indicate an affection in full inflammatory evolution. I prefer to substitute for it the term "coxa-plana" proposed by Waldenstorm; it is short and makes clear the fact that the characteristic of the disease is an acquired articular malformation characterized by the flattening of the superior femoral epiphysis and the regeneration of the epiphyseal osseous nucleus; the articular contacts take place in defective fashion and frequently bring about, under the influence of fatigue or a spurt of growth, painful phenomena comparable to those of all articular malformations. These conclusions have not merely a theoretical interest. It is easy, however, without insisting too much upon them, to deduce from them the matter of practical interest, the treatment of the condition.