DAMASK Trial Team.  Influence of MRI of the knee on general practitioners' decisions: a randomised trial

BACKGROUND: Magnetic resonance imaging (MRI) of the knee for meniscus and ligament injuries is an accurate diagnostic test. Early and accurate diagnosis of patients with knee problems may prevent the onset of chronic problems such as osteoarthritis, a common cause of disability in older people consulting their GP. AIM: To assess the effect of early access to MRI, compared with referral to an orthopaedic specialist, on GPs' diagnoses and treatment plans for patients with knee problems. DESIGN OF STUDY: A multi-centre, pragmatic, randomised controlled trial. SETTING: Five hundred and fifty-three patients with knee problems were recruited from 163 general practices across the UK from November 2002 to October 2004. METHOD: Eligible patients were randomised to MRI or consultation with an orthopaedic specialist. GPs made a concomitant provisional referral to orthopaedics for patients who were allocated to imaging. GPs recorded patients' diagnoses, treatment plans, and their confidence in these decisions at trial entry and follow-up. Data were analysed as intention to treat. RESULTS: There was no significant difference between MRI and orthopaedic groups for changes in diagnosis (P = 0.79) or treatment plans (P = 0.059). Significant changes in diagnostic and therapeutic confidence were observed for both groups with a greater increase in diagnostic confidence (P