Background: To evaluate the clinical e cacy and safety of intra-articular injection with pure platelet-rich plasma (P-PRP) versus those of leukocyte platelet-rich plasma (L-PRP) in treating knee cartilage lesions, we conducted a double-blind, randomized controlled clinical trial with a larger sample and longer followup period.Methods: From October 2019 to October 2020, 95 patients were invited to participate in our study, and 60 (63.2%) were randomized to P-PRP (n = 30) or L-PRP (n = 30) groups. Patients from the two groups were treated with knee intra-articular injections of P-PRP or L-PRP. Visual analog scale (VAS) and Western Ontario and McMaster Universities Arthritis Index (WOMAC) scores were assessed preoperatively and at 6 weeks, 12 weeks, 6 months, and 12 months after intervention.Results: We followed up 27 cases in the P-PRP group and 26 cases in the L-PRP group. No signi cant differences in VAS and WOMAC scores were found between the two groups before the intervention (P>0.05). The WOMAC Pain and VAS-Motions scores of the P-PRP group were signi cantly lower than those of the L-PRP group at 6 weeks after the intervention (P<0.05). While the long-term clinical e cacy of both injections was similar and weakened after 12 months, more adverse events were found in the L-PRP group.Conclusions: The short-term results of our study are encouraging and demonstrate that both L-PRP and P-PRP intra-articular injections reduce pain and improve function in patients with knee cartilage lesions.Compared with the L-PRP injection, the P-PRP injection (which had a lower risk of early in ammation caused by leukocytes) showed better clinical e cacy in the early phase of postoperative rehabilitation and resulted in fewer adverse events. However, long-term clinical e cacy for both injections were similar and weakened after 12 months.Trial registration: ChiCTR1900026365. Registered on 3 October 2019, http://www.chictr.org.cn/showproj.aspx?proj=43911.(RCT) to evaluate the therapeutic e cacy of P-PRP versus that of L-PRP in treating knee cartilage lesions. Methods Trial designThis double-blind, RCT of Evidence Level I compared the safety and e cacy of P-PRP with those of L-PRP in Chinese patients with knee cartilage lesions. This clinical trial was registered at www.chictr.org.cn (ChiCTR1900026365), approved by the Clinical Research Ethics Committees of the hospital of the authors [CZEC (2017)-04], and followed the ethical standards of the institutional and national research committees and the 1964 Helsinki Declaration and its later amendments. Informed consent was obtained from all the participants in the study. From October 2019 to October 2020, 60 patients with knee cartilage lesions were recruited to participate in this study the hospital of the authors. Trial participantsThe following inclusion criteria were used for patient selection: 1. Patients between the ages of 18 and 75 years. MRI clearly indicated articular cartilage injury, and the Kellgren-Lawrence standard knee grade was not more than level-3. 3. Patients with obvi...