Rheumatoid Arthritis (RA) is a chronic disease characterised by symmetric, polyarticular pain and swelling, involving small joints of the hands and feet. RA can lead to irreversible joint damage without treatment, causing disability and impacting daily activities and work productivity. Some patients turn to Chinese Herbal Medication (CHM) for treatment. Since there is currently no well designed randomised controlled trial to support the 'real-world' use of Si Miao Xiao Bi Tang with anti-rheumatic drugs, such as methotrexate, the investigators are conducting a 12-week, randomised double-blinded placebo-controlled trial to determine the efficacy, safety and cost effectiveness of a modified Si Miao Xiao Bi Tang, a type of CHM, in the treatment of patients with active RA.