radiographic progression [2]. Around the turn of the century it
became obvious that radiographic progression could be
stopped completely by current therapy in a large proportion of
patients followed for 1–5 years, and it was appreciated that a
number of patients had lower erosion scores in follow-up films
[3,4]. During the same time period scattered reports were
appearing of repair of erosions, many with equivocal supporting evidence [5-8]. Although a few studies presented images
that were convincing, no studies have been performed to eliminate reader bias or to examine whether there are specific
structural features that permit recognition of repair when the
reader is unaware of the true sequence of films. The observation of negative scores, together with credible reports that
healing might be real, posed the question of whether negative
scores were detecting real structural improvement or artefact
and, if real, whether the observations were clinically relevant or
were trivial