Objective To investigate the effects of intra-articular injection of ropivacaine plus compound betamethasone after arthroscopic debridement for knee osteoarthritis.Methods A total of 164 patients with knee osteoarthritis after arthroscopic debridement were randomly divided into three groups:combination group (n=62) treated by 2 ml sodium hyaluronate and 0.75％ ropivacaine of 5 ml plus 1 ml compound betamethasone,compound betamethasone group (n=54) by 2 ml sodium hyaluronate and 1 ml compound betamethasone,control group (n=48) by simply sodium hyaluronate.The Lequesne Index was used to evaluate the clinical effects before and 1 week,6 weeks and 12 weeks after operation.All patients received at least 12 weeks follow-up Results According to Lequesne Index score criteria,a significant decrease was found in all groups before versus after operation(P＜0.05).The clinical effects in combination group and compound betamethasone group were more improved as compared with control group at 1,6 and 12 weeks after operation (P＜0.05).The effect in combination group was better than compound betamethasone group at 1 and 6 weeks after operation,but not at 12 weeks (P＞0.05).Conclusions The intra-articular injection of ropivacaine plus compound betamethasone after arthroscopic debridement is a good method for relieving pain and improving the knee function.