Objective To investigate the effect of electroacupuncture on articular cartilage and subchon- dral polarization - related protein expression in aged rats. Methods Sixteen 24-month -old SD male rats were randomly divided into old group and electroacupuncture group, with 8 rats in each group. Eight SD male rats aged 6 months were youth group. Electroacupuncture group received electroacupuncture treatment, and the two sides of the“Taixi”, “Zusanli”, “Yanglingquan”, “xuehai”were selected. Electroacupuncture parameters：density wave, sparse wave frequency 3 Hz, dense wave 15 Hz, current intensity 1 mA, once a day, 30 minutes each time, 5 daysa week, consecutive 8 weeks. The other two groups fixed sterile needles with adhesive tape, connected the elec- troacupuncture instrument but did not turn on. After 8 weeks, the content of C-terminal peptide（CTX-Ⅱ) in serum of type Ⅱ collagen was determined by ELISA. Microscopic CT（Micro-CT) was used to detect the microstruc- ture of the left tibia subchondral bone. The left tibial plateau cartilage was observed under light microscope with saffron-solid green staining, and the degree of articular cartilage degeneration was evaluated by modified Mankin′s score. RT-qPCR and Westernblot were used to detect matrix metalloproteinase 1（MMP-1), matrix metallopro- teinase 3（MMP-3), matrix metalloproteinase 13（MMP-13), tumor necrosis factor α（TNF-α), interleukin 1β （IL-1β), and macrophage mannose-receptor（MMR). Expression levels of arginase 1（Arg1) mRNA and protein. Results （1) Compared with the young group, the CTX-Ⅱin the blood of the old group increased（P < 0.05), Saf- fron O-fast green staining showed that the structure of rat cartilage was seriously damaged, cartilage and subchon- dral bone decomposed indistinctly, calcification was severe, multiple tidal lines appeared, the number of cells decreased significantly, split layer appeared, cell morphology and structure was abnormal, and staining was uneven. and the modified Mankin′s score increased（P < 0.05). Bone mineral density, bone volume fraction and number of bone trabeculae decreased（P < 0.05), trabecular thickness and trabecular spacing increased（P < 0.05), MMP1, MMP3, MMP13 mRNA and protein expression increased（P < 0.05), TNF-α, IL-1 β mRNA and protein expres- sion increased（P < 0.05), MMR, Arg1mRNA and protein decreased（P < 0.05). （2) Compared with the senile group, the CTX-Ⅱdecreased in the electroacupuncture group（P < 0.05), The saffron O-fast green staining showed that the cartilage of the rats was slightly smooth and there was no obvious cleavage layer. The number of chondro- cytes in the aged group was higher than that in the aged group, and the staining was more uniform；and the modi- fied Mankin′s score was decreased（P < 0.05). Bone mineral density, bone volume fraction and trabecular number increased（P < 0.05), trabecular spacing decreased（P < 0.05), trabecular thickness tended to decrease（P > 0.05), MMP1, MMP3, MMP13mRNA and protein expression decreased（P < 0.05), TNF-α, IL-1 β mRNA and protein expression decreased（P < 0.05), MMR, Arg1mRNA and protein increased（P < 0.05). Conclusion Electroacupuncture may protect joints by promoting OA articular cartilage and subchondral bone M2 polarization, alleviating articular cartilage degradation and inhibiting subchondral bone osteoporosis in aged rats. [ABSTRACT FROM AUTHOR]