BACKGROUND The interest in shared decision making has increased considerably over the last couple of decades. Decision aids (DAs) can help in shared decision making. Especially when there is more than one reasonable option and outcomes between treatments are comparable. AIM To investigate if the use of DAs decreases decisional conflict in patients when choosing treatment for knee or hip osteoarthritis (OA). METHODS In this multi-center unblinded randomized controlled trial of patients with knee or hip OA were included from four secondary and tertiary referral centers. One-hundred-thirty-one patients who consulted an orthopedic surgeon for the first time with knee or hip OA were included between December 2014 and January 2016. After the first consultation, patients were randomly assigned by a computer to the control group which was treated according to standard care, or to the intervention group which was treated with standard care and provided with a DA. After the first consultation, patients were asked to complete questionnaires about decisional conflict (DCS), satisfaction, anxiety (PASS-20), gained knowledge, stage of decision making and preferred treatment. Follow-up was carried out after 26 wk and evaluated decisional conflict, satisfaction, anxiety, health outcomes (HOOS/KOOS), quality of life (EQ5D) and chosen treatment. RESULTS After the first consultation, patients in the intervention group (mean DCS: 25 out of 100, SD: 13) had significantly ( P value: 0.00) less decisional conflict compared to patients in the control group (mean DCS: 39 out of 100, SD 11). The mean satisfaction score for the given information (7.6 out of 10, SD: 1.8 vs 8.6 out of 10, SD: 1.1) ( P value: 0.00), mean satisfaction score with the physician (8.3 out of 10, SD: 1.7 vs 8.9 out of 10, SD: 0.9) ( P value: 0.01) and the mean knowledge score (3.3 out of 4, SD: 0.9 vs 3.7 out of, SD: 0.6) ( P value: 0.01) were all significantly higher in the intervention group. At 26-wk follow-up, only 75 of 131 patients (57%) were available for analysis. This sample is too small for meaningful analysis. CONCLUSION Providing patients with an additional DA may have a positive effect on decisional conflict after the first consultation. Due to loss to follow-up we are unsure if this effect remains over time.