BACKGROUND: Integrin α5β1 has been shown to be related to acetabular cartilage degeneration due to developmental dysplasia of the hip.OBJECTIVE: To investigate the expression of integrin α5β1 in differently degenerated cartilage tissues of the knee after knee osteoarthritis.METHODS: Seventy-five degenerated articular cartilage specimens at the weight-bearing surface of femoral lateral and medial condyles were removed from patients with knee osteoarthritis who underwent total knee replacement, and were then allotted to four groups based on Mankin's grading system: normal (n=6), mild degeneration (n=24), moderate degeneration (n=26) and severe degeneration (n=19) groups. The expression of integrin α5β1 in each group was detected using real-time PCR, immunohistochemistry and western blot assay.RESULTS AND CONCLUSION: The detected results were consistent in the three kinds of assays, and the expression level of integrin α5β1 was ranked as follows: severe degeneration group > moderate degeneration group > mild degeneration group > normal group (P < 0.05). To conclude, differential expression levels of integrin α5β1 are found in different degenerative degrees of articular cartilage in knee osteoarthritis. Furthermore, the expression level of integrin α5β1 is increased with the degenerative severity.