A method of treating osteoarthritis in a knee includes generating, by an implantable stimulator configured to be implanted beneath a skin surface of a patient, stimulation sessions at a duty cycle that is less than 0.05, and applying, by the implantable stimulator in accordance with the duty cycle, the stimulation sessions to a location that includes at least one of an acupoint labeled ST35, an acupoint labeled EX-LE-4, and a location on a line that intersects the acupoints labeled ST35 and EX-LE-4. The duty cycle is a ratio of T3 to T4. Each stimulation session included in the stimulation sessions has a duration of T3 minutes and occurs at a rate of once every T4 minutes. The implantable stimulator is powered by a primary battery located within the implantable stimulator and having an internal impedance greater than 5 ohms.