OBJECTIVE: To analyze the component law of Chinese medicines in fuming-washing therapy for knee osteoarthritis (KOA), and develop new fuming-washing prescriptions for KOA through unsupervised data mining methods. METHODS: Chinese medicine recipes for fuming-washing therapy for KOA were collected and recorded in a database. The correlation coefficient among herbs, core combinations of herbs, and new prescriptions were analyzed using modified mutual information, complex system entropy cluster, and unsupervised hierarchical clustering, respectively. RESULTS: Based on analysis of 345 Chinese medicine recipes for fuming-washing therapy, 68 herbs occurred frequently, 33 herb pairs occurred frequently, and 12 core combinations were found. Five new fuming-washing recipes for KOA were developed. CONCLUSION: Chinese medicines for fuming-washing therapy of KOA mainly consist of wind-dampness-dispelling and cold-dispersing herbs, blood-activating and stasis-resolving herbs, and wind-dampness-dispelling and heat-clearing herbs. The treatment of fuming-washing. therapy for KOA also includes dispelling wind-dampness and dispersing cold, activating blood and resolving stasis, and dispelling wind-dampness and clearing heat. Zhenzhutougucao (Herba Speranskiae Tuberculatae), Honghua (Flos Carthami), Niuxi (Radix Achyranthis Bidentatae), Shenjincao (Herba Lycopodii Japonici), Weilingxian (Radix et Rhizoma Clematidis Chinensis), Chuanwu (Radix Aconiti), Haitongpi (Cortex Erythrinae Variegatae), Ruxiang (Olibanum), Danggui (Radix Angelicae Sinensis), Caowu (Radix Aconiti Kusnezoffii), Moyao (Myrrha), and Aiye (Folium Artemisiae Argyi) are the main herbs used in the fuming-washing treatment for KOA. (C) 2013 JTCM. All rights reserved.