TENS and Complex Pain: Fibromyalgia, CRPS, Neuropathic Pain, and Central Sensitization

TENS: Much More Than a “Pain Signal Blocker”

TENS is a familiar tool for most healthcare professionals. Accessible, non-pharmacological, and relatively easy to use, it has long been part of the therapeutic options available for pain management. Yet its effectiveness remains a topic of debate. While some patients report meaningful relief, others experience little or no benefit.

Does TENS truly work for complex chronic pain conditions?

The answer is more nuanced than a simple yes or no. To understand why, we need to move beyond the traditional view of TENS as a device that merely "blocks" or temporarily disrupts pain signals.

This concept originates from the well-known Gate Control Theory of pain. By stimulating the sensory nerve fibres responsible for touch and vibration, TENS activates inhibitory mechanisms within the spinal cord. In essence, it helps "close the gate" on certain pain messages before they reach the brain (Martimbianco et al., 2019; Smith et al., 2023). However, decades of research have demonstrated that its effects extend well beyond this mechanism.

Indeed, TENS may influence pain modulation at multiple levels of the nervous system. Near the painful region, it can affect mechanisms involved in pain sensitivity. Within the spinal cord, it may reduce the transmission of nociceptive signals. It can also activate endogenous pain-control pathways within the brain itself (Gibson et al., 2019; Smith et al., 2023). In other words, the effects of TENS are not confined to the area beneath the electrodes.

This broader perspective becomes particularly relevant in conditions such as fibromyalgia, complex regional pain syndrome (CRPS), and certain forms of neuropathic pain. In these disorders, pain is not driven exclusively by tissue pathology; it is also influenced by the way the nervous system processes and regulates sensory information. This distinction fundamentally changes how we think about the clinical role of TENS.

Central Sensitization: When the Nervous System Turns Up the Volume

To appreciate the potential role of TENS in complex pain conditions, it is helpful to understand the concept of central sensitization.

Although the term may sound technical, the underlying idea is straightforward: the nervous system becomes increasingly responsive to incoming signals and amplifies the perception of pain. A useful analogy is that of a stereo system with the volume turned up much higher than intended.

As a result, stimuli that would normally be painless may become painful, a phenomenon known as allodynia. Likewise, stimuli that are already painful may produce a disproportionately intense response, referred to as hyperalgesia.

These changes may also be accompanied by impairments in the body's natural pain-inhibitory systems. In some individuals living with persistent pain, the brain's internal "braking mechanisms" appear less effective at dampening painful inputs (Dailey et al., 2013). Central sensitization plays a particularly important role in fibromyalgia. It may also contribute, to varying degrees and alongside other mechanisms, to certain presentations of CRPS and neuropathic pain. Nevertheless, it would be overly simplistic to attribute all of these conditions solely to central sensitization.

This is where the rationale for using TENS becomes especially compelling.

In individuals with fibromyalgia, Dailey et al. (2013) observed reductions in pain and hypersensitivity during TENS application. Notably, some changes were detected at sites distant from the area being stimulated, suggesting that TENS may alter how the nervous system regulates pain rather than simply producing a localized effect beneath the electrodes.

Fibromyalgia: The Evidence Is Becoming Increasingly Difficult to Ignore

Among the complex pain conditions discussed in this article, fibromyalgia likely has the strongest body of evidence supporting the use of TENS. Early studies showed that even a single TENS session could reduce pain, fatigue, and hypersensitivity in individuals with fibromyalgia (Dailey et al., 2013). Researchers subsequently shifted their attention toward a more practical question:

Can reducing pain help people move more effectively?

A randomized controlled trial published in 2020 found that home-based TENS used during activity significantly reduced movement-evoked pain and fatigue compared with placebo stimulation (Dailey et al., 2020). A systematic review and meta-analysis published in 2023 further highlighted the importance of considering TENS dosage when evaluating treatment outcomes in fibromyalgia (Amer-Cuenca et al., 2023). More recently, Dailey et al. (2026) assessed the addition of TENS to physiotherapy across 28 outpatient clinics. Their findings demonstrated clinically meaningful reductions in movement-related pain, along with improvements in fatigue and overall disease impact. These benefits appeared rapidly and were maintained through the six-month follow-up period.

Why are these findings particularly important?

Because the goal of treatment is not necessarily complete pain elimination. If TENS reduces pain enough to allow patients to walk farther, perform their exercises, or participate more actively in rehabilitation, its clinical value becomes far more significant.

In this context, TENS evolves from a modality aimed solely at symptom relief into a tool that actively facilitates function and participation.

CRPS: A Plausible Mechanism Does Not Guarantee Clinical Effectiveness

Complex Regional Pain Syndrome provides an excellent example of a key principle in evidence-based practice: a treatment that makes physiological sense is not automatically effective in the clinical setting.

CRPS is a multifactorial condition in which numerous mechanisms may contribute to pain and disability. Alterations involving the nervous system, inflammation, cutaneous sensitivity, motor control, and central pain processing may all play a role (Ferraro et al., 2023, 2024). Given these mechanisms, there is a reasonable rationale for considering TENS in some patients. However, the clinical evidence remains limited. Available studies are relatively few in number and generally include small sample sizes. Consequently, systematic reviews continue to report substantial uncertainty regarding the independent effectiveness of TENS for reducing pain and disability in CRPS (Smart et al., 2022).

For this reason, TENS should not be promoted as a treatment for CRPS itself.

A more appropriate role may be as an adjunct to rehabilitation, particularly when it helps patients tolerate activities that would otherwise be difficult to perform. Depending on the clinical presentation, management may include pain education, graded exposure to movement, sensory retraining, and various sensorimotor interventions (Ferraro et al., 2024; Lloyd et al., 2021). In practice, TENS may support CRPS rehabilitation, but it is not a substitute for a comprehensive treatment approach.

Neuropathic Pain: The Right Question Isn't Simply “Does It Work?”

Although the question appears straightforward, the answer is anything but. The term neuropathic pain encompasses a broad range of conditions with distinct underlying mechanisms. Diabetic peripheral neuropathy, for example, differs substantially from neuropathic pain resulting from a spinal cord injury, and these conditions may not respond to treatment in the same way.

This distinction is highlighted in a recent meta-analysis. Overall, the effect of TENS on neuropathic pain was modest and failed to reach statistical significance. However, when investigators examined specific pain conditions, important differences emerged. No clear benefit was observed in diabetic neuropathy, whereas more favourable outcomes were reported in individuals with neuropathic pain associated with spinal cord injury (ElMeligie et al., 2025). These findings should be interpreted cautiously given the variability and overall quality of the available studies. Nevertheless, they emphasize an important clinical principle: Neuropathic pain is not a single entity, and it should not be approached as one when considering a trial of TENS.

Rather than asking whether TENS works for neuropathic pain in general, a more meaningful question is: Which patient, with which type of pain, and for what clinical goal, is most likely to benefit from TENS?

Why Doesn't TENS Produce the Same Results for Everyone?

One of the main reasons the literature on TENS appears inconsistent is that not all TENS interventions are equivalent. Treatment intensity may vary. Session duration may differ. Electrode placement is often inconsistent across studies. Some patients use TENS while resting, whereas others use it during physical activity. Frequency settings and daily treatment exposure also vary considerably.

As a result, two studies may both evaluate "TENS" while examining significantly different interventions.

1. Intensity Matters

Evidence consistently suggests that conventional TENS should be delivered at an intensity that is strong, yet comfortable and non-painful.

In clinical practice, there is often a tendency to reduce intensity excessively in an effort to avoid discomfort. However, stimulation that is barely perceptible may not provide an adequate therapeutic dose. While stronger is not always better, stimulation that is too weak may limit effectiveness.

2. High Frequency Versus Low Frequency: Only One Piece of the Puzzle

Most TENS devices allow clinicians to adjust stimulation frequency. Higher frequencies are commonly used to produce a comfortable sensory sensation, whereas lower-frequency protocols may engage different pain-modulating mechanisms and often require different intensity levels.However, focusing exclusively on frequency may be misleading. There is unlikely to be a single "optimal" frequency that works for everyone. Instead, frequency should be considered alongside treatment intensity, duration of use, electrode placement, and, most importantly, the intended clinical outcome.

3. Timing May Be Just as Important as the Settings

An often-overlooked finding from successful fibromyalgia trials is that TENS was frequently applied during activities known to provoke symptoms (Dailey et al., 2020; Dailey et al., 2026). This detail may be more important than it first appears. If the goal is to reduce movement-evoked pain, assessing TENS only while the patient is at rest may underestimate its clinical value. For many patients, TENS may be most useful when applied during walking, exercise, or other functional activities. In this context, the objective shifts from eliminating pain to making movement more tolerable and participation more achievable.

4. Electrode Placement Still Matters

Electrodes are typically positioned over or near the painful area, or according to a clinically relevant anatomical distribution.

In individuals with complex pain conditions and marked hypersensitivity, comfort and tolerability become critical considerations. Consequently, there is rarely a single electrode placement strategy that is appropriate for every patient presenting with the same diagnosis. Clinical reasoning and patient response should guide positioning decisions.

5. Why Not Test the Response First?

This concept is particularly relevant in fibromyalgia. Vance and colleagues (2021) demonstrated that changes in movement-evoked pain and fatigue during an initial 30-minute TENS session were predictive of longer-term treatment response.

From a clinical perspective, this supports a simple approach: Try it. Measure the response. Reassess.

Rather than basing the decision solely on diagnosis, clinicians can use an individualized trial to determine whether TENS provides meaningful benefits for a specific patient.

Could the Real Value of TENS Lie Elsewhere?

TENS is neither a universal solution nor merely a device that blocks pain signals. Its value lies in how it is integrated into a broader management strategy: with the right patient, appropriate treatment parameters, and a clearly defined clinical objective.

The evidence is particularly encouraging in fibromyalgia, whereas findings remain less convincing in CRPS and vary considerably across different neuropathic pain conditions. One conclusion, however, remains consistent: diagnosis alone is a poor predictor of treatment success. Dosage, context of use, and individual responsiveness all play a critical role. Importantly, the goal of treatment is not always complete pain relief. If TENS reduces pain sufficiently to facilitate movement, support exercise participation, or improve engagement in meaningful activities, it can become a valuable adjunct to rehabilitation.

Ultimately, perhaps the most useful question is no longer: "Does TENS work?"but rather: "How can TENS be used to provide meaningful benefit for this particular patient?"

References

Amer-Cuenca, J. J., Badenes-Ribera, L., Biviá-Roig, G., Arguisuelas, M. D., Suso-Martí, L., & Lisón, J. F. (2023). The dose-dependent effects of transcutaneous electrical nerve stimulation for pain relief in individuals with fibromyalgia: A systematic review and meta-analysis. Pain, 164(8), 1645–1657. https://doi.org/10.1097/j.pain.0000000000002876

Dailey, D. L., Rakel, B. A., Vance, C. G. T., Liebano, R. E., Amrit, A. S., Bush, H. M., Lee, K. S., Lee, J. E., & Sluka, K. A. (2013). Transcutaneous electrical nerve stimulation reduces pain, fatigue and hyperalgesia while restoring central inhibition in primary fibromyalgia. Pain, 154(11), 2554–2562. https://doi.org/10.1016/j.pain.2013.07.043

Dailey, D. L., Vance, C. G. T., Rakel, B. A., Zimmerman, M. B., Embree, J., Merriwether, E. N., Geasland, K. M., Chimenti, R., Williams, J. M., Golchha, M., Crofford, L. J., & Sluka, K. A. (2020). Transcutaneous electrical nerve stimulation reduces movement-evoked pain and fatigue: A randomized, controlled trial. Arthritis & Rheumatology, 72(5), 824–836. https://doi.org/10.1002/art.41170

Dailey, D. L., Vance, C. G. T., Van Gorp, B. J., et al. (2026). Transcutaneous electrical nerve stimulation and pain with movement in people with fibromyalgia: A cluster randomized clinical trial. JAMA Network Open, 9(3), e262450. https://doi.org/10.1001/jamanetworkopen.2026.2450

ElMeligie, M. M., Gomaa, Y. S., Taha, E., et al. (2025). Neuropathic pain relief through transcutaneous electrical neuromuscular stimulation: Insights from a systematic review and meta-analysis of clinical evidence. BioMed Research International, 2025, 5328365. https://doi.org/10.1155/bmri/5328365

Ferraro, M. C., Cashin, A. G., Wand, B. M., et al. (2023). Interventions for treating pain and disability in adults with complex regional pain syndrome: An overview of systematic reviews. Cochrane Database of Systematic Reviews, 2023(6), CD009416. https://doi.org/10.1002/14651858.CD009416.pub3

Ferraro, M. C., O’Connell, N. E., Sommer, C., et al. (2024). Complex regional pain syndrome: Advances in epidemiology, pathophysiology, diagnosis, and treatment. The Lancet Neurology, 23(5), 522–533. https://doi.org/10.1016/S1474-4422(24)00076-0

Gibson, W., Wand, B. M., Meads, C., Catley, M. J., & O’Connell, N. E. (2019). Transcutaneous electrical nerve stimulation (TENS) for chronic pain: An overview of Cochrane Reviews. Cochrane Database of Systematic Reviews, 2019(4), CD011890. https://doi.org/10.1002/14651858.CD011890.pub3

Lloyd, E. C. O., Dempsey, B., & Romero, L. (2021). Complex regional pain syndrome. American Family Physician, 104(1), 49–55.

Martimbianco, A. L. C., Porfírio, G. J., Pacheco, R. L., Torloni, M. R., & Riera, R. (2019). Transcutaneous electrical nerve stimulation (TENS) for chronic neck pain. Cochrane Database of Systematic Reviews, 2019(12), CD011927. https://doi.org/10.1002/14651858.CD011927.pub2

Mokhtari, T., Ren, Q., Li, N., Wang, F., Bi, Y., & Hu, L. (2020). Transcutaneous electrical nerve stimulation in relieving neuropathic pain: Basic mechanisms and clinical applications. Current Pain and Headache Reports, 24(4), 14. https://doi.org/10.1007/s11916-020-0846-1

Smart, K. M., Ferraro, M. C., Wand, B. M., & O’Connell, N. E. (2022). Physiotherapy for pain and disability in adults with complex regional pain syndrome (CRPS) types I and II. Cochrane Database of Systematic Reviews, 2022(5), CD010853. https://doi.org/10.1002/14651858.CD010853.pub3

Smith, T. J., Wang, E. J., & Loprinzi, C. L. (2023). Cutaneous electroanalgesia for relief of chronic and neuropathic pain. The New England Journal of Medicine, 389(2), 158–164. https://doi.org/10.1056/NEJMra2110098

Vance, C. G. T., Zimmerman, M. B., Dailey, D. L., et al. (2021). Reduction in movement-evoked pain and fatigue during initial 30-minute transcutaneous electrical nerve stimulation treatment predicts transcutaneous electrical nerve stimulation responders in women with fibromyalgia. Pain, 162(5), 1545–1555. https://doi.org/10.1097/j.pain.0000000000002144