Diathermy is a therapeutic treatment most commonly prescribed for muscle and joint conditions. It uses a high-frequency electric current to stimulate heat generation within body tissues.

The heat can help with various processes, including:
•    increasing blood flow
•    relieving pain
•    improving the mobility of tissues as they heal
What are the types of diathermy?
There are three main types of diathermy: shortwave, microwave, and ultrasound.
Shortwave diathermy uses high-frequency electromagnetic energy to generate heat. It may be applied in pulsed or continuous energy waves. It has been used to treat pain from kidney stones, and pelvic inflammatory disease. It’s commonly used for conditions that cause pain and muscle spasms such as: 
•    sprains 
•    strains
•    bursitis
•    tenosynovitis
Microwave diathermy uses microwaves to generate heat in the body. It can be used to evenly warm deep tissues without heating the skin. Since it can’t penetrate deep muscles, it’s best suited for areas that are closer to the skin, such as the shoulders.
Ultrasound diathermy uses sound waves to treat deep tissues. Heat is generated by the vibration of the tissue. This promotes blood flow into the area. Ultrasound diathermy is used for: 
•    musculoskeletal sprains
•    strains
•    muscle spasms
•    joint contractures or adhesions
•    neuromas
How does diathermy work?
Diathermy uses high-frequency electric current to produce heat deep inside a targeted tissue. It can reach areas as deep as two inches beneath the skin’s surface.
The diathermy machine does not apply heat directly to the body. Instead, the waves generated by the machine allow the body to generate heat from within the targeted tissue. 
Diathermy is usually part of a complete physical therapy or rehabilitative regimen. Frequency and length of treatments vary. 
What are the benefits of diathermy?
Treating injuries with heat can increase blood flow and make connective tissue more flexible. It can also help minimize inflammation and reduce the incidence of edema, or fluid retention.
By increasing blood flow to the site of an injury, the deep heat generated with diathermy can accelerate healing.
Diathermy is used to treat the following conditions:
•    arthritis
•    back pain
•    fibromyalgia
•    muscle spasms
•    myositis
•    neuralgia
•    sprains and strains
•    tenosynovitis
•    tendonitis
•    bursitis
However, there is still not a lot of evidence to prove that diathermy is the most effective treatment for these conditions.
What are the risks of diathermy?
The electromagnetic energy used in shortwave and microwave diathermy can cause extreme heat in metal devices such as:
•    bone pins
•    dental fillings
•    metal sutures
This could cause burns in the tissue near the implant. The procedure should not be used over these areas to avoid the risk of burning.
During diathermy treatment, you become a part of the electrical field. Touching a bare metal object, including a metal part of the diathermy cabinet, can cause a shock or burn.
Diathermy should be avoided over open growth plates in children.
Who’s qualified for diathermy?
People with implanted metal devices may be at risk for injury if they undergo any type of diathermy. These devices include:
•    pacemaker
•    prosthesis
•    intrauterine device (IUD)
You may not be an appropriate candidate for this treatment if you have:
•    cancer
•    reduced skin sensation
•    peripheral vascular disease
•    tissue with restricted blood supply (ischemia)
•    infections
•    fractured or broken bones
•    bleeding disorders
•    severe heart, liver, or kidney conditions
•    low skin sensation
•    pregnancy
•    perspiration 
•    wound dressings
Diathermy is not considered safe for certain areas of the body. These include:
•    eyes
•    brain
•    ears
•    spinal cord
•    heart
•    reproductive organs
•    genitalia
What is the outlook after diathermy?
After a diathermy treatment, the affected area may feel more flexible. You may be able to participate in physical therapy behaviors more comfortably and for a longer period of time. 
The increased blood flow to the affected area may induce healing and tissue repair.