Thermotherapy is the use of heat to treat symptoms of acute or chronic pain, especially those related to muscle tension or spasm. It is also a common treatment for arthritis, bursitis, tendinitis, back pain, shoulder pain and other kinds of joint pain.

Thermotherapy widens blood vessels and increases blood flow to the skin. It relaxes superficial muscles, decreases muscle spasms and reduces stiffness of joints. Research has shown that it can also block pain receptors.

People often apply heat therapy at home for minor conditions. It is also used in healthcare settings, such as physical therapy, manipulation therapy and occupational therapy.

There are several methods of delivering thermotherapy to the body. They include:

• Warm compresses and hot packs
• Heating pads
• Heat creams and ointments
• Paraffin dips and whirlpool baths
• Ultrasound therapy
• Diathermy, a treatment using microwaves or shortwaves

Moist heat appears to be more effective in treating pain than dry heat, as the moisture allows the heat to penetrate more deeply into the muscle. Thermotherapy is frequently used combination with other therapies to relieve pain, such as hydrotherapy (water therapy). In many cases, cryotherapy (cold therapy) is used to reduce inflammation before thermotherapy is used to increase blood flow to muscles.

Thermotherapy is generally safe but does carry risks if improperly used and is not appropriate for some individuals and conditions. Patients should consult their physician before using thermotherapy.

Thermotherapy is the application of heat to the body to relieve symptoms of acute or chronic pain. It is especially effective in treating pain related to muscle tension or spasm, but can also relieve other types of pain. Moist heat appears to be more effective in treating pain than dry heat because the moisture allows the heat to penetrate more deeply.

Many people use forms of thermotherapy at home to treat minor conditions, such as a hot pack applied to a stiff neck. Thermotherapy is also used in healthcare settings, such as physical therapy, manipulation therapy and occupational therapy. For example, a physical therapist may apply therapeutic ultrasound to a limb before exercise, a massage therapist may apply heated rocks to an aching back, and an occupational therapist may dip an arthritic hand in a warm paraffin bath before addressing fine-motor activities.

Thermotherapy produces several benefits that help relieve pain. Heat can increase blood flow to the skin. Application of heat produces vasodilation (widening of blood vessels), which increases oxygen and nutrient delivery to tissues. Heat relaxes muscles near the surface and makes them more elastic, decreasing stiffness of joints. Research has shown that superficial heat can also block internal pain receptors.

Heat also helps prepare the skin for the application of physical agents. Patients often find the application of moist heat to be soothing and relaxing.

Thermotherapy is often used combination with other therapies to relieve pain. In many cases, cryotherapy (cold therapy) is used to reduce inflammation before thermotherapy is applied to increase blood flow to muscles. Thermotherapy frequently incorporates moisture or water (hydrotherapy). Some forms of electrical therapy supply heat to injured tissues.

Thermotherapy generally should not be used during the first several days after an injury, because heat increases blood flow and may worsen swelling. Heat treatments are inappropriate for some individuals and conditions. For example, people who have impaired sensation (e.g., from neuropathy due to diabetes) are at risk of burns from overuse of thermotherapy. Individuals with poor sensation or other conditions of concern are advised to consult their healthcare provider before trying thermotherapy. Caution should be used not to overdo the therapy, which may burn the skin.

Thermotherapy can be used to treat a number of pain conditions. These include:

• Muscle spasm. Persistent and often painful tension and shortness in a muscle or group of muscles that cannot be released voluntarily.
  
  
• Arthritis. Inflammation of a joint. Types of arthritis that may benefit from thermotherapy include:
  
  
• • Osteoarthritis
  • Rheumatoid arthritis
  • Juvenile arthritis
  • Juvenile rheumatoid arthritis
  • Ankylosing spondylitis
  • Gout
  • Psoriatic arthritis
  • Reiter’s syndrome
    
    
• Sources of back pain, such as a herniated disc. A frequently painful condition in which the cartilage (the tough, elastic, fibrous connective tissue) of an intervertebral disc (discs that serve as cushions between the vertebrae) bulges through its protective covering and presses on a nerve. Most of the time a herniated disc is associated with overlying muscle spasm, which heat therapy decreases.

Other conditions that may be treated with heat include back strain or sprain, degenerative disc disease, sciatica and scoliosis, as these conditions are usually associated with muscle spasm.

• Whiplash and other musculoskeletal types of neck pain.
  
  
• Shoulder pain, such as rotator cuff injuries. The rotator cuff is made up of the muscles and tendons that connect the humerus to the shoulder blade. Tendons in the rotator cuff are normally strong, but they can become inflamed and tear as a result of overuse, wear and tear associated with aging or an accident such as a collision. Another condition that may be eased by application of heat is a frozen shoulder.
  
  
• Other types of joint pain, including many forms of:
  
  
• • Arm pain (e.g., tennis elbow)
  • Leg pain (e.g., restless leg syndrome)
  • Knee pain (e.g., injured anterior cruciate ligament)
  • Foot pain (e.g., plantar fasciitis)

• Tendinitis. Inflammation of a tendon, a fibrous tissue connecting a muscle with its bony attachment.
  

• Bursitis. Inflammation of a bursa, a sac located between a tendon and a bone.
  
  
• Sprain. A painful wrenching or laceration of the ligaments of a joint.
  
  
• Eye pain. An ophthalmologist or other clinician may suggest applying warm compresses to relieve minor conditions such as blepharitis (inflammation of the eyelids).
  
  
• TMJ disorder. Applications of heat may help tender areas.
  
  
• Chest pain. Heat can supply relief from disorders such as costochondritis.
  
  
• Abdominal pain and pelvic pain. Researchers have found that externally applied heat such as hot-water bottles can relieve even deep internal pain for up to an hour by blocking pain receptors.
  
  
• Fibromyalgia. Therapeutic use of heat may help treat this chronic pain condition, characterized by musculoskeletal aches, pain and stiffness, tenderness in soft tissues, general fatigue and sleep disturbances.
  
  
• Other chronic pain disorders, including lupus and myofascial pain syndrome
  
  
• Asthma (see Types and differences)

Heat can also be used as a minimally invasive alternative to surgery. For example, several treatments for benign prostatic hyperplasia use microwaves, lasers or other sources of heat to destroy excess prostate tissue. High-intensity heat is also used to destroy some types of benign and cancerous tumors.

In addition, thermotherapy is used to reduce spasticity in neurological conditions. Recent studies indicate that a combination of thermotherapy and cryotherapy may help stroke patients recover arm function and may ease symptoms in people with heart failure. And other recent research suggests that a microwave form of thermotherapy might benefit women with advanced cervical cancer.

Patients should notify their physician if they suffer pain that is persistent or that fails to respond to treatment. There are several types of thermotherapy. Therapies that may be tried by patients at home include:

• Heat creams and ointments. These popular over-the-counter remedies can provide relief from minor muscle pain. However, these topical treatments do not penetrate very deeply into muscle tissue, making them less effective in treating more significant pain.
  
  
• Hot packs. Heated, cloth-covered pouches with a core of silica gel. They provide relief of pain located in a patient’s trunk, spine or limbs. Hot packs also are used to treat muscle spasms, and the inflammations of tendinitis and bursitis. Variations of this type of therapy include hot water bottles, warm and moist compresses and electric heating pads.

Treatments that are more likely to be administered by a professional include:

• Whirlpool baths. This and other forms of thermal hydrotherapy can also be used to elevate tissue temperature, promote vasodilation (dilation of blood vessels) and help stretch collagen tissue. Patients who have whirlpool baths at home may be able to use these treatments at home.
  
  
• Paraffin treatments. Paraffin (waxy white or colorless solid hydrocarbon mixture used to make lubricants) is mixed with mineral oil in a special basin into which the affected limb is immersed. This treatment can provide relief of arthritic symptoms. These units can also be bought for use at home.

• Ultrasound therapy. A method of applying deep heat to tissues using high-frequency sound waves. Transmission gel, oil or water is applied to the skin covering certain areas of the body. Energy derived from a quartz crystal is then the passed from an applicator through the gel, creating deep heating to soft tissue and bone that increases blood flow and tissue metabolism and raises a patient’s pain threshold. At frequencies from 1 megahertz to 3 megahertz, ultrasound penetrates to deeper structures such as joint capsules, tendons and ligaments and can increase their range of motion. Ultrasound also has powerful anti-inflammatory effects and is effective in treating muscle spasms associated with back pain and various types of neuritis (inflammation of nerves or a group of nerves).
  
  
• Diathermy. In this treatment, microwaves or shortwaves are selectively absorbed by tissues with high water content. Microwave therapy is especially helpful for patients who have sprains, strains, herniated discs, rotator cuff tears or arthritis. Shortwave therapy is often used to treat low back pain, tenosynovitis (inflammation of a tendon sheath) and osteoarthritis of the knee.

Some forms of electrical therapy also provide a thermal effect.

In addition, a new technique called bronchial thermoplasty is being developed to treat asthma, a major cause of chest pain. This method applies heat to the airway through a bronchoscope to relax smooth muscle of the bronchi. Another thermal treatment for asthma is a heat-exchange mask, which may relieve attacks triggered by breathing cold, dry air.

Thermotherapy should generally not be used during the first several days after an injury, because heat increases blood flow and may worsen swelling. For example, soaking a sprained ankle in warm water will increase pain and swelling and prolong the injury, according to the American College of Foot and Ankle Surgeons. Patients are advised to use cold therapy (cryotherapy) first to reduce inflammation before switching to thermotherapy. A physician can help a patient decide when to switch from cryotherapy to thermotherapy.

Heat therapy should not be used on tissue that has received radiation treatment or on tissue that is directly over a cancer site. People with poor sensation, such as some individuals with diabetes, are at increased risk of burns. In addition, pregnant women should not use any form of heat therapy that exposes their fetus to prolonged heat. This includes hot tubs.

Other potential risks associated with thermotherapy include:

• Hot packs. May increase core body temperature and blood flow. In some cases they may aggravate the inflammatory response. In addition, hot packs can cause burns. 
  
  
• Paraffin baths. Paraffin can burn the skin. This therapy should not be used by patients who have active bleeding or infection, neoplasm (abnormal growth of tissue such as a tumor), skin desensitization or vascular insufficiency (insufficient blood flow to a particular part of the body).
  
  
• Ultrasound therapy. May cause cavitation (gas bubble formation in tissue) or superheating of the periosteum (fibrous membrane covering the surface of bones) over bony surfaces. This therapy should not be used near the spine in patients who have had some types of spinal surgery, such as those that expose the spinal cord. It also should not be used over the eye, fluid-filled sacs or neoplasms. Pregnant women should not receive this treatment near their abdomen. Patients who cannot perceive pain or heat should not be treated with ultrasound thermotherapy.
  
  
• Diathermy. There is a risk of tissue burns associated with this therapy. Microwave or shortwave therapy should not be used by patients who are pregnant or who have a pacemaker or any other implants with electrical leads.
  

• Heat creams and ointments. Patients should avoid getting these ointments into their eyes or in contact with sensitive skin.  Patients should not combine other forms of thermotherapy with topical analgesics such as pain-relief ointments. Chemicals in these medications increase blood flow to the skin surface and may hinder the thermoregulatory response of heat redistribution. This can cause burns.

Preparing questions in advance can help patients have more meaningful discussions with their physicians regarding their conditions. Patients may wish to ask their doctor the following questions about thermotherapy:

1. How can thermotherapy help relieve my pain?
   
   
2. Do you recommend thermotherapy for me?
   
   
3. Which form of thermotherapy will be most useful to me?
   
   
4. For how long should I apply heat, and how often?
   
   
5. Which conditions require me to wait before using thermotherapy? How long should I wait?
   
   
6. When and how should I use cold therapy with heat therapy?
   
   
7. Will combining hydrotherapy with thermotherapy offer me greater relief?
   
   
8. Should I perform thermotherapy at home? If so, how?
   
   
9. At what point should I try other treatments or notify you if thermotherapy does not seem to be helping me?
   
   
10. Does thermotherapy pose any risks for me?
    
    
11. Do I have any conditions that rule out use of thermotherapy?