The purpose of this study was to investigate the anti-inflammatory and pain effect according to Achyrantis Radixs administration in osteoarthritis. Experimental groups were divided into 4 groups: group I (n=8, normal group), group II (n=8, monosodium iodoacetate [MIA]-induced osteoarthritis), group III (n=8, MIA-induced osteoarthritis and Achyrantis Radixs administration 100 mg/kg) and group IV (n=8, MIA-induced osteoarthritis and Achyrantis Radixs administration 500 mg/kg). The Achyrantis Radixs administration were assigned 5 days per week for 21 days. Anti-inflammatory and COX-1 expression effect was measured by histology examination and immunohistochemical change. As a result, Achyrantis Radixs administration experimental group III, experimental group IV were significantly effective than experimental group II. Especially, group IV was showed that the most effective response experimental groups. Therefore, we suggested that Achyrantis Radixs administration improve anti-inflammatory effects in MIA-induced arthritis. Especially, Achyrantis Radixs administration 500 mg/kg was the most effective in the anti-inflammatory.