TENS Effectiveness and Knee Osteoarthritis in Humans

TENS is a non pharmacological intervention to control pain. Both high (\>50 Hz) and low (\<10 Hz) frequency TENS are used in the clinic and it is thought that each type works through different mechanisms (see for review Sluka and Walsh, 2003). Hyperalgesia, an increased response to a noxious stimuli, is one component of pain and occurs both at the site of injury, primary hyperalgesia, and outside the site of injury, secondary hyperalgesia. Recent studies in animals with arthritis of the knee show that low and high frequency TENS differentially modulate primary and secondary hyperalgesia. Therefore the investigators hypothesize that TENS will reduce hyperalgesia and pain with movement resulting in increased function.