The efficacy and safety of a polyherbal preparation E-OA-07 was compared against placebo in patients with moderate to severe symptoms of osteoarthritis (OA) of the knee, in a double-blind, randomized, parallel groups study. Male or female subjects with American Rheumatism Association functional class II/III and Kellgren Lawrence grade 2 or 3 OA of the knee, who had moderate to severe OA symptoms as recorded by a score of at least 60 on the modified version of the Western Ontario and McMaster Universities (WOMAC) Osteoarthritis Index, and an overall pain score of at least 70 mm on a 100 mm Visual analogue (VAS) scale were studied. Subjects received 2 capsules of E-OA-07 or placebo twice daily for 12 weeks and paracetamol up to 2 gm per day as rescue medication. Efficacy outcome measures were WOMAC and VAS scores, functional tests for joint mobility and gait, consumption of rescue medication, investigator's global assessment and subjects' opinion. Safety was assessed through incidence of adverse events and subject's assessment of tolerability. After 12 weeks of treatment, there was a significant reduction of WOMAC scores in the E-OA-07 group as compared with placebo (P < 0.01). Mean (±SEM) reductions in WOMAC scores of pain, stiffness, and physical function for E-OA-07 versus placebo were 8.86 (1.77) versus 2.50 (0.76), 3.00 (0.65) versus 0.75 (0.45), and 30.00 (5.22) versus 10.87 (2.18). Significant between-group differences were also observed for VAS scores of pain and stiffness. The symptom alleviating effect of E-OA-07 persisted over a follow-up period of 4 and 6 weeks as VAS pain and stiffness scores continued to remain statistically lower (P < 0.01) in the E-OA-07 group than placebo. Subject's opinion was significantly greater in favor of E-OA-07 than placebo, whereas both groups received favorable responses from investigator. Consumption of rescue medication and tolerability ratings were similar between the 2 groups. One E-OA-07 subject was hospitalized due to accidental fall and withdrawn from the study. No other serious adverse event occurred. The effect of E-OA-07 in relieving moderate to severe symptoms of OA of the knee is well tolerated, superior, and more persistent than placebo.