This is a multi-center, randomized, open-label, parallel-arm phase IV clinical study, for which a total of 300 patients with mild to moderate knee osteoarthritis will be enrolled. In the first 4 weeks (run-in period), the subjects will receive on-demand treatment with Diclofenac Sodium Sustained Release Tablets (DICL-SR) 75mg, quaque die（QD）. After the run-in period, the subjects, if their knee pain has not worsened to a level requiring surgical treatment, will be randomized to two groups in 1:1 ratio: one group receiving Artz® via intra-articular injection (once weekly, for 5 consecutive weeks) in combination with DICL-SR 75mg,quaque die（QD）, for 12 consecutive weeks on demand. The other group receiving DICL-SR 75mg alone,quaque die（QD）, for 12 consecutive weeks on demand. DICL-SR 75mg quaque die（QD） may be administered to the subjects of both groups on demand as long as they have a knee pain. If the knee pain has disappeared, this drug may be withdrawn. However, if the pain occurs again and requires treatment, oral administration of DICL-SR may be resumed. A subject is allowed to withdraw from this study prematurely if unable to tolerate the adverse effects.