Since the original study of this series proved that there are so many possible sources of error from lack of proper appreciation of the appearance of normal joints at all ages, effort has been made to study the hip, knee and shoulder in a manner similar to the methods adopted in studying the elbow. The fact that there are more sources of error in interpreting the elbow than in any other joint in the body encouraged further study.
Francis Howard Williams, in 1902, made the following statement: "The x-rays are of assistance in pointing out delayed union of the epiphyses and when we are familiar with the appearance to be expected of the epiphyses at different ages—that is to say, when we have made a physiological scale, we may find that we have gained a method of estimating the general condition of the younger patients in regard to their development."
COHN I. OBSERVATIONS ON THE NORMALLY DEVELOPING KNEE. Arch Surg. 1922;5(2):395-412. doi:10.1001/archsurg.1922.01110140183010