Physical therapists utilize a variety of interventions for each patient they treat, and their guiding principle is to always combine whichever interventions are most likely to produce a successful outcome. Most treatment programs will include a combination of exercises to increase strength and flexibility, hands–on manual techniques to alleviate pain and improve function, and passive modalities that are also used to reduce pain levels.

One of the more commonly used modalities is called transcutaneous electrical nerve stimulation (TENS), which is a noninvasive therapy that sends a low–voltage electrical current through the nerves to alleviate pain. As a noninvasive treatment, TENS can be seen as an alternative to drug therapy that comes with far fewer side effects. Compared with pain–relieving drugs, the most common side effect of TENS therapy is an allergic skin reaction, which only occurs in about 2–3% of patients.

TENS is administered with a small, battery–powered machine about the size of a pocket radio. The TENS machine has two wires that conduct electrical current called electrodes, which are attached to the skin at the area where the patient is experiencing pain. This creates a circuit of electrical impulses that travels along nerve fibers to relieve pain in that region.

When the TENS machine is turned on, it can be set for different wavelength frequencies depending on the location and degree of the patient’s pain. Once the current is delivered, the patient will often notice an immediate reduction of their pain level. This is either because the electrodes stimulate the nerves in an affected area and signals to the brain that block or scramble normal pain signals, or because the electric stimulation of nerves may help the body produce natural pain killers called endorphins, which block the perception of pain.

Although TENS therapy is used frequently, its efficacy in the real world has been a matter of uncertainty and controversy for many years. Therefore, a large–scale study called a systematic review and meta–analysis was conducted to investigate the efficacy and safety of TENS therapy.

For the meta–analysis, researchers performed a search of 10 major medical databases for high–quality studies that evaluated the use of TENS versus either no treatment, placebo, or some other treatment, for adult patients with clinical pain. This search led to 381 studies being included, with 91 studies comparing TENS to placebo, 10 comparing TENS to no treatment, 61 comparing TENS to standard of care treatments, 67 comparing TENS to other treatments, and 13 comparing high–frequency to low–frequency TENS.

Results from the meta–analysis revealed that there was moderate–certainty evidence that TENS therapy applied within or close to the site of pain elicits clinically important reductions in the intensity of pain during or immediately after treatment. In addition, there were no reports of serious adverse events, which shows that TENS is can be safely used to address pain.

According to researchers, these findings are consistent with clinical experience and long–held expert opinion that TENS provides some patients with immediate short–term pain relief. Researchers also claim that this study should resolve long–term uncertainty about the efficacy of TENS and should encourage physical therapists and other healthcare providers to consider using TENS as an adjunct to core treatment for immediate short–term relief of pain for most musculoskeletal conditions. In addition, patients who are treated with TENS are advised to tailor treatment according to their individual needs to maximize the benefit of this modality.