Relative gene expression in articular cartilage. The relative gene expression of MMP-1, −3, −13 and TIMP-1 was calculated by using quantitative real-time PCR. Data were presented as means ± standard deviation (SD). *P < 0.05, **P < 0.01, ***P < 0.001, compared with vehicle-treated cartilage. (a), (b), (c), (d) represented as the relative gene expression of MMP-1,MMP-3,MMP-13 and TIMP-1 respectively.