ObjectiveHyaluronic acid (HA) intra‐articular injection after arthroscopic knee surgery has been widely applied but its efficacy and safety remain controversial. The aim of this systematic review is to analyze the efficacy and safety of HA intra‐articular injection after arthroscopic knee surgery, and to compare the efficacy of HA with different molecular weights.MethodsWe conducted a systematic literature search in PubMed, Embase, Google scholar and the Cochrane library from inception to 16 September 2022 for English‐written articles, in order to identify randomized controlled trials that evaluated the clinical efficacy and/or safety of HA intra‐articular injection after arthroscopic knee surgery. Then we meta‐analyzed the outcomes of patients given intra‐articular HA injections postoperatively and control patients. We also evaluated the influence of HA with different molecular weights. In every calculation, sensitive analysis was performed. The visual analogue scale (VAS) for pain, Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) and adverse events were selected as the primary outcome measurements, while Lysholm, International Knee Documentation Committee (IKDC) and Tegner score were selected as the secondary outcome measurements. Publication bias of every outcome was evaluated using egger test.ResultsFifteen studies involving 951 knees were included and 12 of them were used to performed the meta‐analysis. The results showed no significant difference between the HA group and control group according to VAS, whether assessed at less (P = 0.90) or more than 6 months (P = 0.55). Besides, there were no statistical differences between the HA group and control group according to subgroup analysis (Ps = 0.77, 0.91 and 0.81 in anterior cruciate ligament reconstruction, meniscectomy and overall groups, respectively). Compared to control group, the overall effect of WOMAC score showed no significant differences (P = 0.25), nor did in two subgroups (P = 0.37 and P = 0.22). Outcomes measured by Lysholm (P = 0.13), IKDC (P = 0.86) and Tegner (P = 0.42) scores showed no significant differences, either. The analysis of the risk of adverse events indicated no increase in HA groups (P = 0.06). We found no significant differences between high‐ and low‐molecular‐weight HA at 6 (P = 0.96) or 12 months (P = 0.93) postoperatively. Two studies failed to pass the sensitive analysis and the reasons were discussed detailly and acceptable publication bias was observed.ConclusionsAlthough HA injection after arthroscopic knee surgery is safe, the available evidence does not support its efficacy in pain relief and functional recovery. Therefore, the application of HA injection after arthroscopic knee surgery is not recommended.