Garcia-Lopez J, et al. - This study was carried out to evaluate risk factors for developing moderate to severe acute postoperative pain (APOP) after total knee replacement (TKR) using the PAIN OUT Questionnaire. Researchers conducted a prospective, multicentre, international cohort study to assess patients’ outcomes with 11-point numerical rating scales (0=null, 10=worst possible). They evaluated the patient and analgesic/anesthetic treatment. They estimated the odds ratio for moderate-severe pain for each variable and whether they were statistically significant in the univariate logistic model, variables were fitted into a multivariate logistic regression model. Cohen´s d coefficient was used to evaluate the effect size. A total of 968 patients were examined in the study. The model distinguished several risk factors for APOP. According to the findings, for higher APOP, preoperative chronic pain, general anesthesia, and the use of opioid analgesics could be predictors. The data may assist establish new strategies for the treatment of pain in TKR. Future trials are required to distinguish acute pain predictors and to develop better strategies of pain management for risk patients.