Table VI.

OARSI–OMERACT definition of relevant structural progression in hip/knee OA

1	Structural progression is optimally defined by plain radiological evaluation of JSW in millimeters
2	The results of the analysis of JSW should be expressed in terms of a dichotomous variable (e.g., progressors yes/no)
3	An absolute change in JSW over a predefined threshold is defining a progressor.
4	The threshold above which a change in JSW can be considered as relevant should be based on the evaluation of the measurement error of the radiological technique.
5	The Bland and Altman technique is the most appropriate one to evaluate the measurement error of the radiological technique evaluating JSW.
6	The pilot study aimed at evaluating the measurement error should be designed to reflect the different characteristics of the primary study in which the analysis of the radiological findings will be based on (patient’s characteristics, centers characteristics, readers …).