Updated osteoarthritis reference standard.

The Kellgren and Lawrence atlas has been the reference standard for radiographic classification of osteoarthritis (OA) for nearly 40 years. Limitations include employment of a global grade, over-emphasis of the osteophyte, and submergence of other features so measurement of disease progression is difficult. Observer bias, drift, and variability cause concern. To address deficiencies and optimize observer accuracy, precision, and agreement, an updated atlas was created. From a photographic set of clinical radiographs, 4 readers selected a subset by consensus. Major radiographic features of hand, hip, and knee OA are graded on a 4-point scale. Using this atlas, it should be possible to individually score each relevant feature in a given joint. It is hoped the atlas will be adopted for population studies, assessment of disease progression, and protocols that evaluate new agents capable of modifying disease.