The TUNEL assay results further confirmed that the overexpression of MMP8 and MMP9 significantly aggravated the apoptosis of chondrocytes in the knee joint of diabetic OA rats (p < 0.01), whereas inhibiting the expression of MMP8 and MMP9 showed a protective effect on chondrocyte apoptosis in diabetic OA rats (Fig. 4c, d). The gene discussed is MMP9; the disease is diabetes mellitus.