There has been growing interest in recent years in the application of the p
rinciples of evidence-based medicine (EBM), although implementation is comp
lex. Scientific, organisational, and behavioural factors all combine to sha
pe clinical behaviour change. Case study based qualitative data are present
ed which illuminate such processes within one clinical setting (elective or
thopaedics), drawn from a larger study. It is suggested that (1) there are
alternative models of what constitutes "evidence" in use; (2) scientific kn
owledge is in part socially constructed; and (3) clinical professionals ret
ain a monopoly of technical knowledge. The implication is that there may be
severe obstacles, to the rapid or broad implementation of EBM.