To evaluate the efficacy and safety of Tongning Gel (TNG) compared to placebo-controlled (PC) for knee osteoarthritis (KOA).A multicentre, randomized, double-blinded, parallel, placebo-controlled, clinical trial was performed in 576 patients (432 patients in the TNG group, 144 patients in the PC group), and 1 in the experimental group withdrew due to nonuse of drug. Patients were randomized to receive TNG or PC applied to knee skin at 3g per time, 2 times per day, which lasted for 3 weeks. The Western Ontario and McMaster Universities Arthritis Index (WOMAC) pain score was used to evaluate the primary efficacy of TNG and WOMAC stiffness and physical function and total scores were used to evaluate the secondary efficacy of TNG. All participants who received at least one dose of study drug were included in the safety analysis. This trial has been registered in Chinese Clinical Trial Registry (no. CTR20131276).Primary efficiency outcome: there were significant differences in the decreased value of WOMAC pain score between two groups (P < 0.05), and the decreased value of WOMAC pain score in the TNG group were better than those in the PC group (P < 0.05). Secondary efficiency outcome: the WOMAC total score, WOMAC stiffness score, WOMAC physical function score, and the decrease of the above indexes of the two groups of patients after treatment were statistically significant (P < 0.05), and the improvement of the above indexes in the TNG group was better than that of the PC group (P < 0.05). Safety Evaluation. A total of 42 adverse events were reported by 29 patients: 25 adverse events reported by 16 patients (3.71%) in the experimental group and 17 adverse events were reported by 13 patients (9.03%) in the control group. And 8 adverse reactions were reported by 6 patients including 2 adverse reactions by 2 patients (0.46%) in the experimental group and 6 adverse reactions by 4 patients (2.78%) in the control group. Two cases of significant adverse events occurred in the experimental group. Both groups had one serious adverse event, respectively, which were not relevant to the intervention.These results of the trial demonstrate that TNG is superior to placebo in the treatment of patients with KOA, and TNG can improve other symptoms of KOA, such as stiffness and physical function. TNG is safe for the treatment of knee osteoarthritis as a whole.