© 2021 John Wiley & Sons LtdStudy Objective: The application of regional anaesthesia techniques as a component of multimodal analgesia in knee arthroscopic surgeries increases the quality of postoperative analgesia. Adductor canal block (ACB) is an effective "motor sparing" analgesia technique used in knee surgeries. This study aimed to evaluate the efficacy of ACB using two different concentrations of local anaesthetic in terms of analgesic requirements and pain density in patients undergoing knee arthroscopy. Design: Prospective, randomised, controlled. Setting: Tertiary hospital. Patients: A total of 60 patients (ASA I-II) were evaluated in three groups, with 20 patients in each group. Interventions: Standardised postoperative analgesia was performed in all groups. In addition, ultrasound-guided ACB (same volume/two different concentrations of bupivacaine: 0.25% vs 0.16%) was applied to the experimental groups. Measurements: Tramadol consumption, rescue analgesic requirement and Numeric Rating Scores (NRS). Main Results: Tramadol requirement in the first 24 hours was significantly higher in the control group (209.5 ± 23.27 mg) (P <.001), and there was no difference between the experimental groups (63 ± 42.06 mg vs 80.5 ± 36.63 mg). Although the mean NRS scores in the first three hours were higher in the control group when compared with both block groups, it was similar in all groups in the following measurements. Conclusion: In arthroscopic knee surgery, ACB interventions with 0.25% and 0.16% concentrations of bupivacaine were similar in terms of postoperative analgesic efficacy, and they increased the quality of multimodal analgesics when compared with the control group.