[Assessment of the American College of Rheumatology criteria for the classification and reporting of osteoarthritis of the knee].

Radiological examination is essential in diagnosing osteoarthritis (OA) of the knee. However, diagnoses that are not based on radiological examination are preferred in epidemiological studies, and the American College of Rheumatology (ACR) has recommended classification criteria for OA of the knee based on clinical examination, and indicated that these classification criteria were appropriate for epidemiological studies. To evaluate the validity of this criteria, we examined the interobserver reproducibility as well as the sensitivity and specificity of the criteria for outpatient attenders complaining knee pain with wide spectrum of rheumatic diseases. As a result, interobserver reproducibility was considered good, but both sensitivity and specificity were slightly lower than the report by ACR in which representative rheumatic diseases such as rheumatoid arthritis were chosen as control. We therefore consider that ACR classification criteria for OA of the knee in of value, but that radiological examination should be preferred in case it is possible.