Electrotherapy for Pain: TENS, Ultrasound and What Each Does

Walk into most physiotherapy clinics in Delhi and you will see the same machines. The wired sticky pads of a TENS unit. The wand of a therapeutic ultrasound device. The larger interferential therapy machines with their coloured screens. Patients often ask me: do these actually work? Or are they just something clinics do because they look like treatment?

The answer is somewhere between the two. It is more nuanced than most clinic websites admit. Some electrotherapy modalities have genuine evidence for specific uses. Others have been used for decades on the basis of tradition rather than research. Recent evidence-based guidelines have significantly narrowed the situations where electrotherapy is recommended.

I am Dr. Richa Gupta, founder of AlignBody Physiotherapy Clinic in Delhi. This post gives you the honest picture: what each modality actually does, what the evidence says, when it is worth using and when a clinic offering you extensive electrotherapy is not doing what evidence-based physiotherapy actually looks like today.

The Big Shift: What Modern Physiotherapy Actually Prioritises

Before we get into the modalities, one thing worth being straight about. Modern physiotherapy has undergone a significant shift away from passive, machine-based treatment towards active, exercise-based rehabilitation. This is not a marketing angle. It is what the evidence supports.

The National Institute for Health and Care Excellence (NICE) in the UK explicitly advises clinicians in its 2021 chronic pain guidelines not to offer TENS, ultrasound or interferential therapy as primary treatment for chronic primary pain, stating that the evidence does not support their use in this context. This position is reinforced in the NICE guidelines for low back pain and sciatica.

This does not mean electrotherapy has no place. It does mean that electrotherapy should be an adjunct to active rehabilitation, not a replacement for it. A clinic that puts you on machines for 30 minutes as your entire treatment is running the physiotherapy of 30 years ago.

How Electrotherapy Actually Works: The Pain Gate Explained

The most common mechanism cited for electrotherapy pain relief is the “pain gate theory,” originally proposed by Melzack and Wall in 1965. Here is what it actually means in plain terms.

Pain signals travel from the site of injury along thin, slow-conducting nerve fibres up to the spinal cord and brain. Non-painful sensations (touch, pressure, vibration, gentle electrical stimulation) travel along larger, faster nerve fibres. When these larger fibres are activated, they can “close the gate” at the spinal cord level, reducing how many pain signals reach the brain.

This is why rubbing your knee after you bump it genuinely reduces the pain. The rubbing activates fast touch fibres that outcompete the slow pain signals at the gate. TENS and other electrical modalities work the same way, delivering controlled sensory stimulation that reduces pain signal transmission.

Electrotherapy also stimulates the release of endorphins (your body’s natural painkillers) and can affect local blood flow, muscle activation and tissue healing depending on the specific modality and settings. Different modalities emphasise different mechanisms.

TENS: Transcutaneous Electrical Nerve Stimulation

TENS is the most familiar electrotherapy modality. Small sticky electrodes are placed on the skin around a painful area and connected to a battery-powered unit that delivers gentle electrical pulses. Most patients feel a tingling or tapping sensation. It is not painful.

What the evidence says

A 2015 Cochrane systematic review found that TENS was better than placebo TENS at reducing the intensity of acute pain in the majority of trials, though the effect was not consistent across all studies. A larger systematic review of 381 trials involving 24,532 participants found moderate-certainty evidence that TENS reduces pain intensity during and immediately after treatment.

For chronic pain the evidence is more mixed. A 2024 meta-analysis found only modest, statistically non-significant benefit for TENS in neuropathic pain overall, though the effect was more meaningful in specific subgroups such as spinal cord injury patients. NICE guidelines do not recommend TENS as a primary treatment for chronic primary pain.

The most honest summary: TENS works for temporary reduction of pain intensity in many patients, does not resolve the underlying condition and is more useful as a self-managed home tool than as a clinic-based treatment.

When TENS is genuinely useful

• Acute muscle pain and soreness as a self-management tool at home
• Chronic low-grade pain for symptom control while working through active rehabilitation
• Post-surgical pain as part of a multimodal pain management approach
• Labour pain as a non-pharmacological option (though evidence is mixed)
• Diabetic peripheral neuropathy in some patients (evidence weaker than for other applications)

Home TENS vs clinic TENS

This is important. Home TENS units are widely available in India for Rs. 800 to 3,000. For the applications above, a home unit used regularly is often more useful than expensive weekly clinic sessions. The device is the same. The location is different. If TENS is going to be part of your pain management, buying a decent home unit and being taught how to use it well is usually a better investment than paying clinic prices for the same therapy.

Therapeutic Ultrasound

Therapeutic ultrasound uses high-frequency sound waves delivered through a hand-held wand pressed against the skin with a coupling gel. The sound waves penetrate 1 to 5 cm into tissue and produce two main effects: a thermal effect (warming deep tissue) and a non-thermal mechanical effect (micro-vibration of cells).

What the evidence says

The evidence for therapeutic ultrasound is more limited than for TENS. It appears to have modest benefit as an adjunct for specific conditions including knee osteoarthritis, calcific tendinopathy of the shoulder and post-surgical soft tissue healing. Even for these applications, the effect on function is generally smaller than the effect on pain. Ultrasound alone does not resolve most musculoskeletal problems.

For chronic low back pain and general soft tissue injury, the evidence for therapeutic ultrasound is weaker. NICE guidelines do not recommend it as a primary treatment. The 2021 NICE chronic pain guideline advises against using it for chronic primary pain.

When therapeutic ultrasound is worth considering

• As part of a treatment programme for knee osteoarthritis combined with exercise
• Calcific tendinopathy of the shoulder where it may help break down calcium deposits
• Sub-acute soft tissue injuries as an adjunct to exercise-based rehabilitation
• Trigger point work to warm and soften tissue before manual therapy

A clinic that uses ultrasound as your entire treatment session is not using it well. Ultrasound as an adjunct to focused manual therapy and exercise is where it earns its place.

Interferential Therapy (IFT)

Interferential therapy uses two medium-frequency electrical currents that intersect at the tissue level, producing a lower-frequency stimulation deeper in the body than TENS reaches. The mechanism is similar to TENS but the depth of penetration is greater, making it theoretically more suitable for deeper tissue pain.

What the evidence says

Direct comparison studies between TENS and IFT for chronic low back pain have generally found no meaningful difference in outcomes. Both produce short-term pain reduction. Neither resolves the underlying problem. The NICE 2021 chronic pain guidelines advise against IFT for chronic primary pain along with TENS and ultrasound.

For acute muscle pain and post-injury pain, IFT can be a useful short-term intervention as part of a broader programme. The reason it remains widely used in Indian physiotherapy clinics is partly historical and partly because many patients specifically request electrotherapy sessions.

Neuromuscular Electrical Stimulation (NMES)

NMES uses stronger electrical stimulation than TENS to directly cause muscle contraction. Unlike TENS which mainly targets sensory nerves for pain relief, NMES targets motor nerves to activate muscles that are inhibited or weak.

What the evidence says

NMES has more consistent evidence than most electrotherapy modalities for specific applications. Post-surgical quadriceps activation (after ACL reconstruction or knee replacement), stroke rehabilitation for muscle reactivation and rehabilitation of muscles inhibited by pain or disuse all have reasonable evidence bases.

When NMES is genuinely useful

• Post-surgical muscle reactivation particularly after knee surgery
• Stroke rehabilitation for motor recovery in the affected limb
• Muscle atrophy from disuse or immobilisation
• Chronic pain conditions with associated muscle inhibition
• Selective muscle activation in rehab of specific movement patterns

The Direct Comparison: What Each Modality Actually Does

When Electrotherapy Is a Reasonable Adjunct

Based on the current evidence, electrotherapy has a legitimate place in physiotherapy for the following scenarios:

• Short-term pain relief during the first 2 to 3 weeks of a physiotherapy programme, to make active rehabilitation more tolerable
• Post-surgical rehabilitation where muscle activation is genuinely inhibited (NMES)
• Specific conditions with reasonable evidence such as knee osteoarthritis with ultrasound, spinal cord injury pain with TENS
• Home self-management of ongoing pain (TENS specifically)
• Preparation for manual therapy where heating tissue makes hands-on work more effective
• Patient preference and comfort where a patient specifically wants a modality as part of their care and has been fully informed about the evidence

When Electrotherapy Is Being Overused

Warning signs that a clinic is over-relying on electrotherapy rather than doing evidence-based physiotherapy:

• Every session begins with 20 to 30 minutes of TENS or IFT as the main treatment
• You are not given a home exercise programme
• The therapist spends most of the session away from you attending other patients while machines run
• Sessions are booked for months on end without clear progression or reassessment
• Progress plateaus but the same electrotherapy is repeated at every visit
• No manual therapy, exercise or movement assessment is included

Effective physiotherapy for musculoskeletal problems centres on assessment, active rehabilitation, hands-on manual therapy where indicated and patient education. Electrotherapy fits around this framework, not at the centre of it.

Safety and Contraindications

Electrotherapy is generally very safe when used appropriately. The specific contraindications that matter:

• Pacemakers and implanted cardiac devices: electrical modalities near the chest can interfere with device function
• Pregnancy: avoid electrotherapy over the abdomen, lower back and pelvis. Some upper body applications may be acceptable with practitioner guidance
• Active cancer in the treatment area: thermal modalities in particular are contraindicated over active tumours
• Epilepsy: some modalities may need modification or medical clearance
• Deep vein thrombosis: electrotherapy over an active DVT can dislodge the clot
• Open wounds or active skin infection at the electrode site
• Loss of sensation in the treatment area (nerve damage): patients cannot feel the intensity properly and can be burned
• Metal implants near the treatment area for some modalities (ultrasound particularly)
• Bleeding disorders or anticoagulant medication for deep-penetrating modalities

The India Context

Electrotherapy remains more widely used in Indian physiotherapy clinics than in many Western countries. This is partly cultural (patients expect machines as part of “proper” treatment), partly economic (electrotherapy sessions are billable and machines are a fixed cost the clinic wants to recoup) and partly because dedicated exercise-based rehabilitation takes more clinician time than plugging someone into a machine.

Home TENS units are widely available at chemists and online in the Rs. 800 to 3,000 range. Basic dual-channel units for around Rs. 1,500 are perfectly adequate for home pain management. Larger clinic-grade combination units (TENS + IFT + ultrasound in one machine) sold direct to consumers are usually not worth the investment for a home setting.

If a clinic in Delhi is offering you a treatment package that consists mainly of electrotherapy for a musculoskeletal problem, ask specifically about what active rehabilitation is included. If the answer is unclear, consider whether that clinic is offering current best practice.

Combining Electrotherapy with the Rest of Physiotherapy

Where electrotherapy fits in a modern physiotherapy programme, it works alongside these other elements:

• Clinical assessment identifying the actual mechanism of the problem
• Active exercise programme targeting specific movement deficits
• Manual therapy and myofascial release for hands-on tissue work
• Dry needling where trigger points are contributing
• Movement retraining and postural correction
• Patient education about self-management and prevention
• Progressive return to full function

Read our related guides on common conditions where this integrated approach applies: why lower back pain hurts, neck pain and cervical stiffness, shoulder pain physiotherapy and sciatica pain treatment.

Frequently Asked Questions

Does TENS actually reduce pain or just distract from it?

Both, honestly. TENS activates the pain gate mechanism at the spinal cord, which genuinely reduces the pain signal reaching the brain rather than only distracting from it. It also stimulates endorphin release which further reduces pain perception. The pain reduction is real. What TENS does not do is treat the underlying cause of the pain. This is why it is a good pain management tool but not a stand-alone treatment for musculoskeletal conditions.

Should I buy a home TENS unit or get clinic sessions?

For most pain management purposes, a home TENS unit is a better investment than repeated clinic sessions delivering the same therapy. A decent home unit costs Rs. 800 to 3,000. Twenty clinic sessions of TENS at Rs. 500 to 1,500 each costs Rs. 10,000 to 30,000 for the same modality. Where clinic-based electrotherapy makes more sense is when combined with skilled manual therapy, exercise prescription and clinical assessment as part of an integrated programme. Standalone electrotherapy without other treatment components is not worth clinic pricing.

Is therapeutic ultrasound the same as diagnostic ultrasound?

The technology is similar but the intensity, frequency and purpose are different. Diagnostic ultrasound (the pregnancy scan) uses very low intensity to generate images. Therapeutic ultrasound uses higher intensity to generate heating and tissue effects and does not produce images. They cannot be substituted for each other. Do not attempt therapeutic use with a diagnostic device or vice versa.

How long does electrotherapy pain relief last?

The pain-relief effect of TENS and IFT typically lasts from 15 minutes to a few hours after the session ends. Cumulative effects with regular use over weeks can extend this. Therapeutic ultrasound and NMES do not produce immediate pain relief but can support tissue healing and muscle activation over a course of treatment. None of these modalities provide lasting pain relief on their own. The lasting relief comes from resolving the underlying problem, which usually requires exercise and movement re-education.

Are there any side effects of electrotherapy?

Serious side effects are rare when contraindications are respected. Common minor effects include skin irritation under electrode pads (usually from the sticky adhesive rather than the current), temporary tingling or mild soreness after treatment and rarely, a headache in patients sensitive to electrical stimulation. Skin burns are possible if intensity is set too high, if electrodes are placed on skin with reduced sensation or if the equipment is faulty. A properly conducted treatment does not cause burns.

Can I do electrotherapy every day?

Home TENS can be used multiple times daily as needed for pain management. Sessions of 20 to 30 minutes 2 to 4 times daily is a reasonable pattern. Clinic-based modalities like ultrasound and IFT are typically used 2 to 3 times per week during an active treatment phase, then reduced. Continuous daily clinic-based electrotherapy for months on end is not evidence-based and represents a plateau in treatment rather than progress.

Does electrotherapy work for chronic conditions like arthritis?

For knee osteoarthritis, therapeutic ultrasound and TENS have some evidence for pain reduction as part of a multimodal treatment programme that includes exercise, weight management (if relevant) and lifestyle modification. Neither modality on its own produces meaningful improvement in arthritis. For other chronic conditions the picture is more mixed. Chronic pain conditions increasingly are managed with active, exercise-based approaches supplemented by education about pain science, with electrotherapy as an optional adjunct for symptom management rather than as core treatment.

Electrotherapy is a useful tool with a limited but real place in modern physiotherapy. TENS is a genuine pain-management aid, especially as a home self-management tool. Therapeutic ultrasound and NMES have evidence for specific applications when used correctly. Interferential therapy is broadly similar to TENS in effect and mechanism.

What none of these do is fix the underlying cause of a musculoskeletal problem on their own. That is why modern physiotherapy has moved decisively toward exercise-based rehabilitation with electrotherapy as an occasional adjunct, rather than as the centrepiece of treatment.

If you have a pain problem that has been treated only with electrotherapy for weeks or months without meaningful progress, it is worth booking an assessment with a physiotherapist practising the current evidence-based approach. Book at AlignBody for a proper assessment and a treatment plan that puts electrotherapy in its right place, not at the centre. Our clinics run from Jagriti Enclave in East Delhi and Vasant Vihar in South Delhi. Read more about our approach to how physiotherapy can speed up your recovery from injuries.

Has your physiotherapy so far consisted mainly of lying still while machines run? Or has it included active exercise, manual therapy and progressive rehabilitation? Your answer determines whether you are getting current best-practice care.