The objective of the study was to assess the analgesic effects of dexamethasone (DEX) added to peripheral nerve block in knee surgery. We searched for relevant randomized controlled trials (RCTs) in PubMed and the Cochrane Database of Systematic Reviews. The latest search was done on September 11, 2024. Search terms included knee surgery, regional anesthesia, and DEX. Data extraction, statistical analysis, and risk of bias assessment followed established protocols. Seven RCTs with 551 patients were included. In the DEX 4 mg group, no reduction of pain at rest was found. However, for the DEX 8 mg group, pain management at rest was more effective; the mean difference (MD) with 95% CI was –0.34 [–0.50, –0.18]. For pain with movement, the model favors the DEX 4 mg group (MD with 95% CI was –1.03 [–1.84, –0.22]). Only one study reported the differences in pain intensity scores with movement between the DEX 8 mg and control groups. For morphine consumption, the model did not reveal any reduction in the DEX 4 mg group (MD –0.68 [–1.87, 0.5]) or DEX 8 mg group (MD –10.44 [–23.92, 3.03]). Pain with movement may be reduced with a lower dose, and pain without movement with a higher dose of DEX.