Although the usage of acupuncture for pain has increased in recent years, the mechanisms of acupuncture analgesia (AA) remain unclear. The lack of suitable experimental animal models for persistent pain, which show clear AA, has been the major stumbling block in the investigation of the physiological mechanisms of AA. In the present study, we test AA in two knee arthritis models induced by injection of CFA or carrageenan as persistent pain models. After induction of arthritis, the rat subsequently showed a reduced stepping force of the affected limb for the next several days. Electroacupuncture (EA) was applied to an acupuncture point each on the contralateral forelimb for 30 minutes under gaseous anesthesia. After the termination of EA, behavioral tests measuring stepping force were periodically conducted during the next several hours. EA produced a significant improvement of stepping force of the foot lasting for at least 2 hours when applied to LR2 in CFA model, and applied to ST36 in carrageenan model, but both points did not produce any significant effects in each other model. Further experiments showed that intraperitoneal pretreatment of naltrexone, a non-selective opioid antagonist, did not reduced the EA-induced improvement of stepping force in both of two models. These data suggest that EA produce analgesic effect in knee arthritic pain and the analgesic effect is specific to the acupuncture point depending on painful conditions.