Validity, reliability, and applicability of seven definitions of hip osteoarthritis used in epidemiological studies: a systematic appraisal.

OBJECTIVE To summarise and review articles addressing the quality (validity, reliability, applicability) of seven commonly used definitions of hip osteoarthritis (OA) for epidemiological studies in order to use it primarily as a classification criterion. METHODS Medline and Embase were searched and articles studying the validity, reliability, or applicability of the definitions of hip OA were selected. Two reviewers independently extracted data on the quality of the seven definitions. RESULTS Review of the literature showed the validity of the various definitions of hip OA, in particular, has barely been investigated. Minimal joint space (MJS) demonstrated the highest (intra- and interrater) reliability, and showed the highest association with hip pain and restricted internal rotation compared with the other definitions of hip OA. The reliability of the Kellgren and Lawrence grade and the index according to Lane is comparable with that of the MJS, but the construct validity should be investigated more thoroughly. The reliability and validity according to the Croft grade were inferior to the MJS, the Kellgren and Lawrence grade, and the index according to Lane. Despite precise and extensive development, the ACR criteria showed poor reliability and poor cross-validity (agreement between three ACR criteria sets) in a primary care setting. CONCLUSIONS The reliabilities of MJS, Kellgren and Lawrence, and the index according to Lane were comparable, but the MJS had the highest relationship with hip pain in a male population. Considering how often definitions of hip OA are used, it is surprising that the validity has been so poorly investigated, and the validity needs to be studied more thoroughly.