75 patients with knee osteoarthritis were randomized to receive a high frequency transcutaneous electrical nerve stimulation (TENS) treatment, a low frequency TENS treatment, or a placebo TENS treatment. The primary outcomes were pain, pain sensitivity and function. Results indicated that the HF- and LF-TENS groups showed improvements in pressure pain threshold. However, the TENS treatments did not have any effect on cutaneous pain measures. Improved subjective pain ratings at rest and during movement, in both active and placebo TENS groups, suggest the presence of a placebo effect. The clinical implications of this study is unclear, additional research is necessary.