[Purpose] We examined the impact of exercise on the expression pattern of nerve growth factor in the spinal cord of rats with induced osteoarthritis of the knee joint. [Subjects and Methods] To produce monosodium iodoacetate-induced arthritis, rats were administered 3 mg/50 µL monosodium iodoacetate through the interarticular space of the right knee. The animals were randomly divided into four groups: rats sacrificed 3 weeks after 0.9% saline solution injection (shame group, n = 10), rats sacrificed 3 weeks after monosodium iodoacetate injection (control group, n = 10), rats with 4 weeks rest from 3 weeks after monosodium iodoacetate injection (no exercise group, n = 10), and rats with 4 weeks treadmill training from 3 weeks after monosodium iodoacetate injection (exercise group, n = 10). Serial coronal sections of the lumbar spine were cut and processed for immunohistochemistry. [Results] The expression of nerve growth factor was significantly increased in the EG compared with the SG, CG, and NEG. [Conclusion] Increased nerve growth factor expression in the spinal cord due to exercise-induced stimulation can be effective in treating chronic pain. Such treatment will contribute not only to improving the joint function of patients with chronic pain but also their quality of life.