The present invention relates to methods for treating inflammatory diseases accompanied by bone destruction, comprising the step of administering a viral vector comprising a gene which inhibits signal transduction mediated by fibroblast growth factor-2 (FGF2)-FGF receptor 1-Ras-Raf-MAP kinase to a diseased region. Furthermore, the present invention relates to therapeutic compositions for inflammatory diseases accompanied by bone destruction, which comprise these vectors. By inhibiting FGF2 signal transduction through local administration of viral vectors, both inflammation and bone destruction in inflammatory bone destruction were simultaneously suppressed. The present invention provides disease-specific and effective therapeutic methods, and therapeutic compositions for inflammatory diseases such as osteoarthritis, for which therapy has so far been difficult.