The system of grading presented here more nearly meets the requirements set forth than have others presented in the literature. This system attempts to standardize all important findings, so that various observers can arrive at the same grade for any given hip. It makes possible a comparison of the same hip at various ages which, as will be shown in Part II, gives valuable information. Those findings of least accuracy are grouped together and do not lessen the accuracy of the whole. The physical findings are more accurate than the symptomatic observations, but they too will not be graded by two observers exactly alike, since an estimate of the degree of limp and of hip motion will vary even between two careful observers.

The roentgenographic grade depends for the most part on actual measurements which can be checked by more than one observer and, although these measuremensts admittedly vary somewhat with changes in projection of the roentgenograms, it is believed that this variation can be minimized by attention to details. The same plan of grading results, with some modification of the basic roentgenographic factors, can be used in evaluating the long-term results of therapy in other hip conditions.