This study investigated the anti-inflammatory effects of mixed extracts of Achyranthes japonica Nakai (AJ) and Aralia continentalis Kitagawa (AC) (ratios of 1:2, 1:3, 1:5, 2:1, 3:1 and 5:1) on RAW264.7 macrophages and evaluated the anti-inflammatory effects of the mixed extracts of AJ and AC by measuring IL-1β, IL-6, and TNFα using the ELISA kit assay. In particular, the formation of nitric oxide (NO) was found to decrease in the group treated with the combined extracts of AJ and AC at all ratios. In particular, extracts of ratio of 2:1 (AJ:AC) deceased the formation of NO level that is approximately 60% of the group treated with only lipopolysaccharide (LPS). Also, extracts of ratio of 2:1 (AJ:AC) reduced the production of IL-1β, IL-6, TNFα and PGE2 with statistical significance. Volunteers over the age of 50 who complain of discomfort in knee joints were selected as the experimental subjects. The subjects took daily administration of 2000 mg of the combined extracts of ratio of 2:1 (AJ:AC) for 12 weeks. A survey (VAS (Visual Analog Scale), WOMAC (Western Ontario and McMaster Universities Osteoarthritis Index)) was conducted after the 12 weeks of oral administration. The experimental group showed the change between each visit and baseline time compared with the control group. In the intention-to-treat (ITT) analysis, VAS score and WOMAC stiffness score decreased significantly. And the WOMAC total score and function score tended to decrease. In the per-protocol (PP) analysis, the WOMAC stiffness score was significantly decreased and the VAS and WOMAC total and function scores were decreased. There was no significant difference in all parameters of ITT and PP in radiological examinations.