Figure 1 Histopathological changes in rat knee joint cartilage after monosodium iodoacetate injection and fraxetin intervention
Note： A， B， and C are the staining results of hematoxylin-eosin， safranin O–fast green， and toluidine blue in the knee cartilage tissue of three groups of rats （scale bar = 300 μm， the black arrow in the picture points to the surface of the knee cartilage）. The blank group refers to rats that were first injected with 50 μL of normal saline into the right knee joint cavity， followed by intra-articular injections of 50 μL of normal saline for 7 consecutive days； the model group refers to rats that were injected with one time injection of 50 μL fresh prepared monosodium iodoacetate （60 mg/mL）in the right knee joint cavity to induce osteoarthritis， followed by injections of 50 μL of normal saline for 7 consecutive days； the intervention group refers to rats that were injected with one time injection of 50 μL fresh prepared monosodium iodoacetate （60 mg/mL）in the right knee joint cavity， followed by fraxetin injections （5 mg·kg^-1·d^-1， dissolved in 50 μL of normal saline） for 7 consecutive days.

Figure 2 Micro-CT imaging of the rat knee joint after monosodium iodoacetate injection and fraxetin treatment
Note： A， B， C， and D represent micro-CT images of the knee joints of three groups of rats， scanned at the levels of 3D reconstruction， the tibial platform， the subchondral bone， and specific cross-sectional regions， to assess bone structure and evaluate osteoarthritis changes. The blank group refers to rats that were first injected with 50 μL of normal saline into the right knee joint cavity， followed by intra-articular injections of 50 μL of normal saline for 7 consecutive days； the model group refers to rats that were injected with one time injection of 50 μL fresh prepared monosodium iodoacetate （60 mg/mL）in the right knee joint cavity to induce osteoarthritis， followed by injection of 50 μL of normal saline for 7 consecutive days； the intervention group refers to rats that were injected with one time injection of 50 μL fresh prepared monosodium iodoacetate （60 mg/mL）in the right knee joint cavity， followed by intra-articular injections of fraxetin （5 mg·kg^-1·d^-1， dissolved in 50 μL of normal saline） for 7 consecutive days.

Figure 3 Expression of inflammation-related proteins in rat serum and knee cartilage after fraxetin treatment
Note： A-D， show the serum levels of IL-6， IL-1β， TNF-α， and COMP detected by ELISA. E shows the expression of p38 MAPK， JNK， p-p38 MAPK， and p-JNK proteins in knee cartilage tissues detected by Western blotting. F and G show the ratios of p-JNK/JNK and p-p38 MAPK/p38 MAPK， reflecting the phosphorylation levels of JNK and p38， which indicate the activation levels of the corresponding pathways. The blank group refers to rats that were first injected with 50 μL of normal saline into the right knee joint cavity， followed by intra-articular injections of 50 μL of normal saline for 7 consecutive days； the model group refers to rats that were injected with one time injection of 50 μL fresh prepared monosodium iodoacetate （60 mg/mL）in the right knee joint cavity to induce osteoarthritis， followed by intra-articular injections of 50 μL of normal saline for 7 consecutive days； the intervention group refers to rats that were injected with one time injection of 50 μL fresh prepared monosodium iodoacetate （60 mg/mL）in the right knee joint cavity， followed by intra-articular injections of fraxetin （5 mg·kg^-1·d^-1， dissolved in 50 μL of normal saline） for 7 consecutive days. There were 6 rats in each group （n=6）. Compared with the blank group， ^*P<0.05； compared with the model group， ^#P<0.05.