PURPOSE Acute knee injury is common, and MRI is often only used when non-operative management fails because of limited availability. We investigated whether early MRI in acute knee injury is more clinically and cost-effective compared to conventional physiotherapy and reassessment. METHODS All patients with acute indirect soft tissue knee injury referred to fracture clinic were approached. Recruited patients were randomised to either the MRI group early MRI within 2 weeks or the control group conventional management with physiotherapy. Patients were assessed in clinic initially, at 2 weeks and 3 months post-injury. Management costs were calculated for all patients until surgical treatment or discharge. RESULTS Forty-six patients were recruited 23 in the MRI and 23 in the control group. Male sex and mean age were similar in the two groups. The total management cost of the MRI group was £16,127 and control group was £16,170, with a similar mean cost per patient (NS). The MRI group had less mean physiotherapy (2.5 ± 1.9 vs. 5.1 ± 3.5, p CONCLUSIONS Early MRI in acute knee injury facilitates faster diagnosis and management of internal derangement at a cost comparable to conventional treatment. Moreover, patients had significantly less time off work with improved pain, activity limitation and satisfaction scores. LEVEL OF EVIDENCE II.