OBJECTIVE: Knee arthroscopy has a good effect on mild to moderate knee osteoarthritis, but the lavage fluid will take away a lot of the original synovial fluid. It is still controversial whether synovial fluid can be further improved by postoperative injection of sodium hyaluronate. This study is designed to evaluate the efficacy of arthroscopy combined with sodium hyaluronate compared with arthroscopy alone for knee osteoarthritis. METHODS: The relevant literature was searched from CNKI, Wangfang, VIP, CBM, PubMed, Web of Science, EMBASE, and Cochrane Library from inception to March 27, 2020. The randomized controlled trials on arthroscopy combined with sodium hyaluronate for knee osteoarthritis were included. Included studies were evaluated using the Cochrane system evaluation method. Meta-analysis was performed using RevMan 5.3 software. The primary outcomes included Lequesne score, Lysholm score, WOMAC score, and visual analogue scale score. The secondary outcomes included tumor necrosis factor-α, interleukin-1β, and interleukin-6 in synovial fluid. RESULTS: A total of 31 randomized controlled trials were included with 1 350 cases. Meta-analysis results showed that in primary outcomes: (1) Lequesne score was better in the combined group than that in the control group at 1 week after surgery (MD=-0.33, 95%CI: 0.67 to -0.00, P=0.05), after the full treatment course (MD=-1.00, 95%CI:-1.34 to -0.66, P < 0.000 01), 3 months after surgery (MD=-1.04, 95%CI:-1.44 to -0.64, P < 0.000 01). (2) Lysholm score was better in the combined group than that in the control group at 1 week after surgery (MD=5.84, 95%CI:4.79-6.88, P < 0.000 01), after the full treatment course (MD=9.21, 95%CI:6.93-11.49, P < 0.000 01), 3 months after surgery (MD=9.14, 95%CI:6.34-11.94, P < 0.000 01), half year after surgery (MD=10.14, 95%CI: 6.50-13.78, P < 0.000 01), 1 year after surgery (MD=11.54, 95%CI:9.92-13.16, P < 0.000 01). (3) WOMAC score was better in the combined group than that in the control group at 1 year after surgery (MD=-18.38, 95%CI:-28.53 to -8.23, P=0.000 4). Visual analogue scale score was better in the combined group than that in the control group at 1 week after surgery (MD=-0.91, 95%CI:-1.11 to -0.72, P < 0.000 01), after the full treatment course (MD=-0.97, 95%CI:-1.23 to -0.72, P < 0.000 01), 3 months after surgery (MD=-0.41, 95%CI: -0.52 to -0.31, P < 0.000 01). (4) Lequense score was better in the combined group after the full treatment course compared with that after only one week (MD=1.47, 95%CI: 1.14-1.80, P < 0.000 01). (5) The combined group could better reduce the contents of tumor necrosis factor-α, interleukin-1β, and interleukin-6 in the synovial fluid (P ≤ 0.05), which could better control the inflammation. CONCLUSION: Arthroscopy combined with sodium hyaluronate can achieve a better short- and medium-term curative effect in knee osteoarthritis than arthroscopy alone. However, more high-quality studies are needed to verify the above conclusions. [ABSTRACT FROM AUTHOR]