Abstract: Objective To evaluate the effect of intra-articular injection with platelet-rich plasma on early stage knee osteoarthritis. Methods A total of 17 patients(21 knees) with stage Ⅰ-Ⅲ osteoarthritis(Keligren Lawrence classification) from June to October in 2018 in the first medical center of Chinese PLA General Hospital were included in this study. All the patients had received autologous PRP injection(3 ml) into the affected knee joint every week for totally 3 injections. The visual analogue scale(VAS), Western Ontario and McMaster Universities Osteoarthritis Index(WOMAC) were used to evaluate knee function before and at 3 days, 1 month and 3 months after injection. The adverse reactions were recorded, and the repeated ANOVA was used to evaluate the difference betweens pre-and post-injection. Results Seventeen patients(21 knees) with average age of 46.8±15.79(22-66) years were followed up for 3 months, and no severe adverse reaction was observed. The VAS score before and at 3 days, one month and 3 months after injection were 5.2±1.8, 2.8±1.3, 2.3±1.3, 2.4±1.2, and the WOMAC were 30.8±15.4, 14.9±6.1, 14.5±6.5, 13.9±5.8, respectively. There were significant differences in the VAS score and WOMAC score between pre-and post-injection(all P < 0.01). Conclusion Autologous platelet rich plasma is effective in treatment of early stage knee osteoarthritis. The pain symptoms can be alleviated at 3 days after injection.