Outcome measurement in osteoarthritis clinical trials.

The clinical assessment of outcome in osteoarthritis (OA) clinical trials is highly dependent on the use of valid, reliable, and responsive measurement techniques. Despite several decades of clinical studies, and a half-century of development in clinical metrology, we still lack international standards of measurement for OA trials. There have, nevertheless, been several very encouraging developments. In particular, the Osteoarthritis Research Society and the 5th WHO/ILAR Task Force have discussed issues of standardization. The Western Ontario and McMaster Universities Osteoarthritis Index and Lequesne Index have been proposed as important outcome measures. Finally, data have recently been published on observer variability, variance estimation, and sample size determination for OA trials.