Background:　Primary　osteoarthritis　(OA)　is　a　polygenic　disease.　To　investigate　the　gene　expression　profile　of　cartilage　and　synovium　from　osteoarthritis　and　healthy　rats　using　cDNA　microarray　is　beneficial　to　recognize　the　pathogenesis　of　osteoarthritis　and　provide　evidence　for　gene　therapy　of　osteoarthritis.　Objective　:　The　present　study　aimed　to　investigate　the　gene　expression　profile　of　the　cartilage　and　synovium　of　chronic　arthritis　and　healthy　rats　through　cDNA　microarray　assay,　and　identify　the　differentially　expressed　genes.　This　study　may　be　helpful　for　understanding　the　role　of　differentially　expressed　genes　in　osteoarthritis　and　the　gene　polymorphism　of　osteoarthritis.　Methods:　A　total　of　24　male　Wistar　rats　were　randomly　divided　into　control　group　and　osteoarthritis　group　(n　=　12　per　group).　The　synovial　and　cartilage　were　obtained　and　total　RNA　was　extracted.　cDNA　microarray　assay　was　performed　to　identify　the　differentially　expressed　genes,　and　cluster　analysis　was　conducted.　Results　and　Conclusion　:　A　total　of　82　differentially　expressed　genes　were　identified,　among　which　27　were　up-regulated　and　55　down-regulated.　Gene　microarray　assay　is　effective　to　identify　differentially　expressed　genes　and　may　find　out　novel　osteoarthritis　associated　genes.　Multiple　genes　are　involved　in　the　pathogenesis　of　osteoarthritis.　The　differentially　expressed　genes　provide　important　information　for　further　studies　on　the　pathogenesis　of　osteoarthritis　and　gene　therapy　of　osteoarthritis.