Radiological assessment of osteo-arthrosis.

In a previous study (Kellgren and Bier, 1956), three sets of x rays of the hands were used to assess interand intra-observer differences in interpreting changes of rheumatoid arthritis. Wide disagreement between observers was found, and it was concluded that, to ensure maximum uniformity in grading x rays in field surveys and therapeutic trials, all readings should be made by the same observer, preferably at a single session. The advisability of having a set of standard reference films was also considered.