Objective:To explore the effect of electroacupuncture combined with close-to-bone needling on expression of cartilage cell HDAC4 and Runx2 in rabbits with knee osteoarthritis(KOA). Methods:Totally 40 New Zealand rabbits were randomly assigned to control group(without any treatment

n=10)and modeling group(n=30). Knee osteoarthritis model was established by Hulth-Telhag and was evaluated by X-ray examination. Rabbits with successful modeling were randomly divided into model group(n=10)

normal thrust needing groups(NTN group

n=10)and eletroacupuncture with close-to-bone needling group(CBN group

n=10). Electroacupuncture was performed in NTN group and CBN group at "neixiyan"

"waixiyan"

"Zusanli"

"yinlingquan"and "liangqiu"points 20 minutes once time per day for 4 courses of treatment

one of which was 10 days with the interval of 3 days. After 4 weeks

the knee joint function was observed based on Lequesne algofunctional index. HE staining and Toluidine blue staining were conducted for the morphologic observation of rabbit articular cartilage and the ultrastructure was observed under transmission electron microscope. Immunohistochemistry and Western blot were used to assess the expressions of HDAC4 and Runx2 in rabbit articular cartilage. Results:No significant change was observed in NTN group

CBN group and model group. Compared with those of control groups

the passive range of motion of the knee in model group significantly decreased

cartilage cell number decreased and arranged in disorder

while the expression of HDAC4 protein decreased and the expression of Runx2 protein increased(all P=0.000). Compared with those in model group

the passive range of motion of the knee in NTN group and CBN group increased

and the chondrocytes arranged in line

while the expression of HDAC4 protein increased and the expression of Runx2 protein decreased(all P=0.000). There was notable differences of each index between NTN group and CBN group(all P=0.000). Conclusion:Electroacupuncture with close-to-bone needling method could inhibit hypertrophic differentiation of chondrocyte through regulating the expression of HDAC4 and Runx2 of cartilage cell

which may be the possible therapeutic mechanism of KOA. Electroacupuncture with close-to-bone needling method is more effective than normal thrust needing for KOA probably due to more intensive needling sensation.