Radiographic assessment. Introduction: existing methodology

Plain radiograph is the most accepted imaging technique to assess structura l changes of osteoarthritis and it is proposed as 'surrogate' of outcome of the disease process. The existing radiographic methodology is well standar dized with respect to its technique for investigation of hip, knee and hand joints, including advice on the most appropriate views, patient positionin g, X-ray beam alignment, quality control. Quantitation of joint space narro wing is currently proposed as the primary variable in studies of disease pr ogression for hip and knee, while semi-quantitation of this same parameter or of bone changes by published atlases have to be intended as secondary va riables, or outcomes in hand studies. Unfortunately, the review of studies that evaluated the longitudinal rate of joint space narrowing indicates tha t the yearly change may be very small (<0.1 mm/year) and of doubtful clinic al significance. This underlines the need for further refinement in the def inition of the radiographic outcome in prospective clinical trials.