Objective To investigate the effect of internal heat-type acupuncture needle on the expression of osteoprotegerin(OPG)

receptor activator of NF-κB ligand(RANKL)

and receptor activator of NF-κB(RANK) in knee osteoarthritis(KOA) rabbits

so as to explore its mechanisms in relieving KOA. Methods Thirty New Zealand rabbits were randomly divided into control

model and treatment groups

with 10 rabbits in each group. The KOA model was established by using Hulth method. The rabbits of the treatment group received internal heat-type acupuncture needles(42 ℃) on the left hind limb 20 min

once a week for 4 weeks. The behavioral scores were assessed according to the pain severity

gait

joint motion range and articular swelling severity in reference to the modified Lequesne's methods. Toluidine Blue staining was performed to observe the structure of the subchondral bone and to analyze the difference of morphometric parameters. The protein and mRNA expressions of OPG

RANKL and RANK were detected by Western blot and real-time PCR

respectively. Results Compared with the control group

the Lequesne total score

the separation degree of trabecular bone

the protein and mRNA expressions of RANKL and RANK in subchondral bone tissues were significantly increased in the model group

while the percentage of trabecular bone area

number of trabecular bone

the expression of OPG protein and mRNA were decreased(P<0.05

P<0.01). The above indexes were all reversed in the treatment group relevant to those of the model group(P<0.05). Conclusion The internal heat-type acupuncture needle therapy can improve the motor function of rabbits with KOA

which may be related to its effects in up-regulating the expression of OPG and down-regulating the RANKL and RANK in subchondral bone tissue.