Force plate analysis was used to describe the effect of acupuncture on right knee osteoarthritis (OA) in a seven-year-old hound breed dog weighing 27 kg. The acupuncture treatment was performed twice a week for 3 weeks. Ground reaction forces (GRFs) and subjective clinical scores in both hind limbs were obtained prior to and 72 hours after each treatment. Right vertical peak force was increased as the dog was acupunctured. Although their sensitivity was lower than that of the GRF data, the subjective clinical scores reflected an improvement. In addition, vertical peak force of normal left hind limb was also increased during this trial. These results indicate that gait analysis may be valuable objective method in future evaluation of acupuncture for OA of the stifle joint.