RESUMEN
OBJECTIVE: To assess the effectiveness of a Patient Decision Aid (PtDA) for knee osteoarthritis. METHOD: Randomized controlled trial, in which 193 patients were allocated to the PtDA or usual care. Outcome measures were the Decisional Conflict Scale (DCS), knowledge of osteoarthritis and arthroplasty, satisfaction with the decision-making process (SDMP) and treatment preference, assessed immediately after the intervention. At 6 months, the same measures were applied in non-operated patients, whereas those who underwent arthroplasty completed the SDMP and the Decisional Regret Scale (DRS). RESULTS: The PtDA produced a significant immediate improvement of decisional conflict (MD = -11.65, 95%CI: -14.93, -8.37), objective knowledge (MD = 10.37, 99%IC: 3.15, 17.70) and satisfaction (MD = 6.77, 99%CI: 1.19, 12.34), and a different distribution of preferences (χ2 = 8.74, p = 0.033). Patients with less than secondary education obtained a stronger effect on decisional conflict (p = 0.015 for the interaction) but weaker for knowledge (p = 0.051). At 6 months, there were no significant differences in any variable, including the rate of total knee replacement. Operated patients showed a low level of regret, which was not affected by the intervention. CONCLUSION: The PtDA is effective immediately after its application, but it shows no effects in the medium-term. Future research should investigate which subgroups of patients could benefit more from this intervention, as well as the longitudinal evolution of decision-related psychological variables.