Abstract: Objective To compare the long-term outcomes of arthroscopy and non-surgical therapy in patients with knee synovial plica syndrome (SPS). Methods Thirty-one patients with knee SPS undergoing arthroscopic surgery and 27 SPS patients undergoing conservative treatment with articular cavity injection of sodium hyaluronate (control group) were compared for visual pain score (VAS) and the Lysholm score before and after the operation. The patients were followed-up for more than 5 years, and the long-term outcomes were compared using Kaplan-Meier survival analysis. Results VAS and the Lysholm scores in both groups were significantly lowered after treatment (P<0.05). The postoperative VAS score was significantly lower while the Lysholm score significantly higher in arthroscopic surgery group than in the control group (P< 0.05). Arithmetic mean and the median time of curative effect maintenance were 49 and 43 months in arthroscopic surgery group, as compared with 33 and 29 months in the control group, respectively; the cumulative effect maintenance rate in arthroscopic surgery group was significantly higher than that in the control group (χ2=4.933, P=4.933). Conclusion Arthroscopic treatment produces better therapeutic effect on knee joint SPS and ensures longer long-term therapeutic effect maintenance than conservative treatment.