What Is Diathermy? Types, Uses, Procedure, and Safety
Updated: 6 days ago
Written and medically reviewed by Dr. Baraa Alnahhal, MD · Last reviewed: October 2026 · How we review
Quick Answer: What is diathermy?
Diathermy is a therapy that uses high-frequency electrical energy, delivered as radio waves, microwaves or sound waves, to heat tissues below the skin. It is used to ease chronic pain, stiff muscles, spasms, arthritis and swelling, and to support recovery from sprains and strains. A session takes about 15 to 20 minutes, and burns are the main risk. [1]
What the research says
Short-wave diathermy eased knee arthritis pain more than standard care. A 2026 review of 17 trials (1,372 people) found improvements in pain, walking, function and stiffness; it relieved pain better than conventional therapy, but ultrasound relieved pain slightly better than short-wave, and some evidence was very low certainty. (Zhang et al., Physiotherapy Theory and Practice, 2026) [2]
Pain improved, but day-to-day function did not. A meta-analysis of 8 randomized trials (542 patients) found short-wave therapy reduced knee arthritis pain compared with sham or no treatment (SMD −0.53), with no significant change in physical function and no extra side effects. (Wang et al., Clinical Rehabilitation, 2017) [3]
The warmth seems to matter. A review of 7 trials found small, significant benefits for pain and muscle performance only when the treatment produced a noticeable local heat sensation. (Laufer et al., Osteoarthritis and Cartilage, 2012) [4]
Key takeaways
Diathermy means "deep heating." It warms muscles, joints and other tissues beneath the skin, not your whole body. [1]
The three main types are short-wave, microwave and ultrasound diathermy. [1]
It is used for chronic pain, arthritis, stiff muscles, muscle spasms, fibromyalgia, swelling (edema) and sprain or strain recovery. [1]
Metal in or on the body is the key safety issue. Implants, pacemakers, pregnancy and several health conditions can rule it out. [1]
It is usually an add-on to other care, such as physical therapy, not a stand-alone treatment. [1]
What is diathermy?
Diathermy is a therapeutic treatment that uses high-frequency electric currents to produce heat in the tissue layers under your skin. The word itself means "deep heating." [1]
That heat helps muscles and joints relax, lowers inflammation and swelling, and improves blood flow to the treated area. [1]
How does diathermy create heat inside the body?
Diathermy creates heat by making the particles inside your tissues move. The machine's energy sets electrons moving between atoms, and that movement produces warmth in a small, targeted area. [1]
Think of it like a relay race: each runner passing the baton works harder and warms up. Your atoms "pass" electrons in a similar way, and the activity generates heat. You may feel gentle warmth spreading from the treated spot. [1]
What are the types of diathermy?
The three main types of diathermy are short-wave, microwave and ultrasound. Each delivers energy in a different way, but all three aim to heat tissue below the surface. [1]
Type | Energy used | How it is applied | How heat is made |
Short-wave (radio-wave or high-frequency) | Electromagnetic radio waves sent in short pulses | Two plates (electrodes) placed on either side of the body area | The waves pass between the plates and warm the tissue in between |
Microwave | Very small electromagnetic waves (microwaves) | A large, flexible, lamp-like applicator held close to the skin | Microwaves travel into the tissue under the skin |
Ultrasound | Sound waves | A probe moved over gel on the skin | The sound waves make tissue vibrate, which creates heat |
Source for table: [1]
What is surgical diathermy?
Surgical diathermy is a different use of the same principle. During an operation, surgeons use high-frequency currents to cut tissue or stop bleeding by clotting blood. It is not a pain or rehabilitation treatment. [1]
What conditions does diathermy treat?
Diathermy treats conditions that involve pain, muscle tension, inflammation or slow healing in soft tissues and joints. Common uses include: [1]
Stiff muscles
Fibromyalgia
Recovery from sprains and strains
Who is a good candidate for diathermy?
A good candidate for diathermy is someone with ongoing pain, tight muscles or inflammation who has no conditions that make deep heating unsafe. You may be a candidate if you: [1]
Live with chronic pain
Want to improve blood flow to one area of the body
Have stiff, tense muscles or muscle spasms
Have a condition that causes inflammation
Want to heal faster after a sprain or strain
Your healthcare provider will review your health history before deciding whether diathermy is right for you. [1]
Who should not have diathermy?
People with metal in their body, certain serious illnesses or pregnancy should usually not have diathermy, because these conditions raise the risk of burns or injury. [1]
Reason to avoid diathermy | Examples |
Metal in the body | Sutures, pins, pacemakers, implanted nerve or brain stimulators (even if turned off), intrauterine devices (IUDs), dental fillings |
Cancer | Any active cancer |
Skin or tissue damage | Infections, open wounds, broken bones |
Serious organ disease | Severe heart disease or kidney disease |
Pregnancy | Any stage |
Bleeding problems | A long-term bleeding condition |
Source for table: [1]
If you have a pacemaker, read more in our guide to permanent pacemakers and always tell every provider that you have one.
What happens during a diathermy session?
A diathermy session involves removing all metal, lying still on a metal-free surface and letting the machine send heat into the target area. Here is what each stage looks like. [1]
Before the session
You remove all metal, including jewelry, glasses, earrings and clothing with zippers, because metal reacts with the machine.
You may be asked to change into a gown.
You sit or lie on a special chair or table that has no metal in it.
Your provider positions the machine near the area being treated. [1]
During the session
Short-wave: two plates sit on the front and back of the area, keeping the radio waves contained to that spot.
Microwave: the applicator is placed close to your skin and sends microwaves into the tissue.
Ultrasound: your provider spreads gel on your skin and holds a probe over it, much like an ultrasound scan.
You stay relaxed and very still while the machine works. [1]
After the session
Many people notice changes straight away, such as: [1]
Less pain or tension
Relaxed muscles
Warmth in the treated area
Less swelling
Better flexibility and range of motion
Faster healing of sprains and strains
How long does a diathermy session take?
A diathermy session takes about 15 to 20 minutes on average. The time can be longer when symptoms are more severe, and the exact length depends on the type of diathermy used. [1]
What are the benefits and risks of diathermy?
Diathermy's main benefits are pain relief, better circulation, relaxed muscles and less swelling, while its main risk is a burn. [1]
Benefits | Risks |
Relieves pain | Burns, if heat stays in one spot too long |
Increases blood flow | A painful shock if you touch metal during treatment |
Relaxes muscles | Injury if metal implants, such as a pacemaker, react to the machine |
Reduces swelling and inflammation |
Source for table: [1]
To lower these risks, your provider watches the treatment closely to make sure it is safe and working. Always tell them about any metal in your body before you start. [1]
Research also supports a pain benefit for knee arthritis, with smaller or no gains in day-to-day function. [2][3]
What is recovery like after diathermy?
Recovery after diathermy is usually immediate, and most people return to their normal routine right after the appointment. [1]
Depending on why you are being treated, you may need several sessions. Your provider will explain how often you should come in. [1]
Diathermy is usually a supplemental treatment. It is often combined with other care, especially physical therapy. [1]
When should you call a doctor after diathermy?
You should contact your healthcare provider right away if you feel a burning sensation under your skin. [1]
It is also wise to book a follow-up visit after treatment so your provider can check whether diathermy helped your symptoms. [1]
Diathermy at a glance
Question | Answer |
What it is | Deep heat therapy using radio waves, microwaves or sound waves |
Main types | Short-wave, microwave, ultrasound |
Common uses | Arthritis, chronic pain, stiff muscles, spasms, fibromyalgia, sprains and strains, edema |
Session length | About 15–20 minutes |
Does it hurt? | It is described as painless; you may feel warmth |
Main risk | Burns |
Key safety rule | No metal on or in the body |
Recovery | Back to normal activities right away |
Source for table: [1]
Conclusion
Diathermy is a simple, usually painless way to deliver heat deep into muscles and joints. It can ease pain, relax tight muscles, reduce swelling and support recovery after sprains and strains, and it often works best alongside physical therapy. [1]
The most important step is safety screening. Metal implants, pacemakers, pregnancy, cancer and several other conditions can make diathermy unsafe, so share your full health history before your first session. [1]
Next step: If pain, stiffness or swelling is limiting your day, ask your healthcare provider whether diathermy could fit into your treatment plan. To keep learning, read our guides on chronic pain and knee osteoarthritis.
FAQ
What is diathermy used for?
Diathermy is used to relieve chronic pain, relax stiff muscles and spasms, and reduce inflammation and swelling. It also helps people recover from sprains and strains and is used for arthritis and fibromyalgia. [1]
Is diathermy painful?
Diathermy is generally painless. Most people feel only gentle warmth in the treated area, but you should tell your provider straight away if you feel burning. [1]
How long does a diathermy session last?
A diathermy session lasts about 15 to 20 minutes on average. More severe symptoms may need a longer session. [1]
What are the side effects of diathermy?
The most common risk of diathermy is a burn if heat stays in one place too long. Touching metal during treatment can also cause a painful shock. [1]
Can you have diathermy with a pacemaker or metal implant?
Diathermy is usually not recommended if you have a pacemaker or other metal in your body, such as pins, sutures, an IUD or dental fillings. Metal reacts with the machine and can cause injury. [1]
Can you have diathermy during pregnancy?
Diathermy is not recommended during pregnancy. Your provider can suggest a safer option. [1]
What is the difference between short-wave and ultrasound diathermy?
Short-wave diathermy heats tissue with radio waves passed between two plates, while ultrasound diathermy uses sound waves from a probe to make tissue vibrate and warm up. In knee arthritis research, ultrasound relieved pain slightly better than short-wave. [1][2]
How many diathermy sessions will I need?
The number of diathermy sessions depends on the reason for treatment. Many people need several sessions, and your provider will set the schedule. [1]
Does diathermy work?
Diathermy may help ease pain and stiffness for some people, but results vary and some studies are low quality. It works best as part of a broader plan, such as physical therapy and exercise.
Can diathermy burn the skin?
Yes, burns can happen, especially near metal or in areas with poor feeling. Tell your therapist right away if the area feels too hot or painful during treatment.
Related Reading
Physical Therapy: Enhancing Mobility, Strength, and Recovery explains how physical therapy improves strength and movement.
TENS Unit: How Transcutaneous Electrical Nerve Stimulation Relieves Pain describes how mild electrical pulses can ease pain.
What Is Arthritis? A Plain-Language Guide to the Most Common Joint Problem in the World covers arthritis types, symptoms and treatment options.
What Is Myofascial Pain Syndrome? A Plain-Language Guide to the Muscle Pain That Won't Quit explains muscle trigger point pain and how it is treated.
References
Cleveland Clinic. Diathermy: Meaning, Types & Benefits. Cleveland Clinic. Last updated April 24, 2023. https://my.clevelandclinic.org/health/treatments/24926-diathermy
Zhang S, Zhang H, Yu Y, et al. Shortwave diathermy for managing knee osteoarthritis: A systematic review with meta-analysis. Physiotherapy Theory and Practice. 2026. Epub ahead of print. PMID: 42348367. https://doi.org/10.1080/09593985.2026.2688499
Wang H, Zhang C, Gao C, et al. Effects of short-wave therapy in patients with knee osteoarthritis: a systematic review and meta-analysis. Clinical Rehabilitation. 2017;31(5):660-671. PMID: 28118736. https://doi.org/10.1177/0269215516683000
Laufer Y, Dar G. Effectiveness of thermal and athermal short-wave diathermy for the management of knee osteoarthritis: a systematic review and meta-analysis. Osteoarthritis and Cartilage. 2012;20(9):957-966. PMID: 22659070. https://doi.org/10.1016/j.joca.2012.05.005
Medical disclaimer
This article is for general educational purposes only and does not replace professional medical advice, diagnosis or treatment. Always talk with a qualified healthcare provider about your symptoms and before starting any new treatment.
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