Objective：We aimed to identify the clinical effects of platelet-rich plasma（PRP）on knee osteoarthritis.Methods：We performed a matched case control research for patients with osteoarthritis in our hospital from October 2017 to June 2019，according to gender and age. Both PRP group and the control group enrolled 43 cases. All the patients were evaluated by the severity of osteoarthritis according to Keligren-Lawrence classification. The PRP group received an intra-articularly PRP injection intraoperatively，while the control group received arthroscopic treatment only. Both groups had the same rehabilitation plan after surgery. The pain and knee function were assessed by the VAS score and WOMAC score at baseline，1，3，6 and 12 months after the treatment. The PRP-related complications were recorded during the follow-up.Results：All enrolled patients were available for 12 months follow-up. No serious complication was found in both groups. The VAS and WOMAC scores of both PRP group and the control group after the treatment were significantly lower than those at the baseline. The VAS and WOMAC scores of PRP group were significantly lower than those of the control group at 1 and 3 months but not at postoperative 6 and 12 months after the treatment. For paitents with K-L grade 2，the VAS and WOMAC scores of PRP group were significantly lower than those of the control group at 1，3 and 6 months，but not at 12 months after the treatment. Meanwhile，for paitents with K-L grade 3，the VAS and WOMAC scores of PRP group were significantly lower than those of the control group only at 1 months，but not at 3，6 and 12 months after the treatment.Conclusion：For patients with osteoarthritis，PRP treatment could relieve pain symptoms and restore knee joint function with limited course. PRP has longer duration of efficacy in patients with lower K-L grade.