Background: Adductor canal block (ACB) provides effective analgesia after arthroscopic knee surgery. However, there is insufficient data regarding whether ACB should be performed before or after inflation of a thigh tourniquet. We aimed to investigate the efficacy of ACB performed before and after placement of a thigh tourniquet and evaluate associated quadriceps motor weakness. Methods: ACB was performed before tourniquet inflation in the PreT group, and it was performed after inflation in the PostT group. In the PO group, ACB was performed at the end of surgery after deflation of the tourniquet. Results: There were no statistically significant differences between the groups in terms of demographic data. There was no statistically significant difference among the three groups in terms of total postoperative opioid consumption (P = 0.513). Patient satisfaction and the amount of rescue analgesia administered were also not significantly different between the groups. There was no significant difference in terms of static and dynamic visual analog scale scores between the groups (for 24 h: P = 0.306 and P = 0.271, respectively). The incidence of motor block was higher in the PreT group (eight patients) than in the PostT group (no patients) and the PO group (one patient) (P = 0.005). Conclusions Using a tourniquet before or after ACB did not result in differences in terms of analgesia quality; however, applying a tourniquet immediately after ACB may lead to quadriceps weakness.