Ultrasound therapy uses high-frequency sound waves to produce heat that can reduce pain. It may be used to treat conditions such as musculoskeletal injuries, arthritis and fibromyalgia.

Typically performed during physical therapy, occupational therapy or manipulation therapy, ultrasound therapy provides deep heat to the affected tissues. It may help:

• Stimulate healing without causing irritation
• Speed metabolism and improve circulation
• Break up and soften scar tissue and adhesions
• Reduce chronic inflammation or swelling
• Reduce irritation to nerve roots
• Enhance the body’s natural healing process

Ultrasound therapy is generally safe. However, it does carry some risks, such as the potential for burns. Patients are advised to consult with their physician before receiving therapeutic ultrasound. It is not recommended in some cases, such as over a pacemaker, near the abdomen of a pregnant woman, or over the skull, eyes, heart or reproductive organs. It is generally avoided in areas affected by cancer.

Therapeutic ultrasound differs from diagnostic ultrasound, which uses less-intense sound waves to create images of internal structures.

Ultrasound therapy is a type of thermotherapy (heat treatment) that helps relieve some types of acute and chronic pain. A console provides an electrical current via a coaxial cable to a hand-held applicator (transducer). The applicator contains a quartz crystal that expands and contracts, producing sound waves, which are then transmitted to the patient’s skin and into the body.

Therapeutic ultrasound is typically delivered at frequencies between 0.8 to 3 megahertz (800 to 3,000 kilohertz). Lower frequency provides deeper penetration, up to about 2 inches (5 centimeters). The sound waves cause molecules in the tissues to vibrate, producing heat and mechanical energy. This allows for deep heating of tissues such as muscles, tendons, ligaments, joint capsules and bone.

Ultrasound therapy is a form of diathermy, the deep heating of tissues. Other types of diathermy include microwave and radiofrequency (short-wave) or high-frequency devices. At a tissue depth of 2 inches, diathermy devices should produce heat between 104 and 114 degrees Fahrenheit (40 to 45.5 degrees centigrade) for a maximum of 20 minutes, according to the U.S. Food and Drug Administration.

There are two approaches when using ultrasound therapy: continuous wave and pulsed wave. In cases where heating is not desired, such as with acute inflammation or with wound care,  intermittent (pulsed) is used, rather than the typical continuous application, which provides mechanical effects such as increased permeability of cell membranes and possibly repair of tissues.

Therapeutic ultrasound is different from diagnostic ultrasound, which uses lower-intensity sound waves to produce images of internal structures rather than to create thermal and mechanical actions. In addition, intense highly focused ultrasound can be used to eliminate unwanted tissue, such as kidney stones, gallstones, benign prostatic hyperplasia and some types of tumors including uterine fibroids and (in some countries) prostate cancer.

The thermal effects of ultrasound therapy have been found to be beneficial in the treatment of musculoskeletal injuries, breaking down scar tissue and helping to stretch tendons. The use of ultrasound as deep heat therapy may also be accompanied by electrical stimulation of the muscle. This results in mechanical pumping, which would promote the removal of products of increased metabolism, and treat muscle spasms and microscopic tissue adhesions.

Therapeutic ultrasound may be used to treat many other conditions as well. It has anti-inflammatory effects that can relieve the pain and stiffness of arthritis and some other inflammatory conditions. It may be used to treat impingement (compression) of nerve roots and various types of neuritis (nerve inflammation) and may be useful in the care of post-traumatic injuries.

However, ultrasound therapy has some risks. Unlike diagnostic ultrasound, it is not used near the abdomen of a pregnant woman because the higher intensity of sound waves may harm a developing fetus. It may also have negative effects on cancerous tissues or areas of bone overgrowth. It is also avoided over bony prominences and, in children, over epiphyseal plates of growing bones. Ultrasound therapy is not advised for patients who cannot perceive pain and heat, such as some patients with diabetic neuropathy.

Ultrasound therapy may be used to treat musculoskeletal pain and other disorders. These conditions include:

• Muscle spasm. Persistent and often painful tension and shortness in a muscle or group of muscles that cannot be released voluntarily. Contractures from increased muscle tone can also be treated with ultrasound. Treatment produces extensibility of the tissue, thereby increasing its range of motion.
  
  
• Nerve root impingement (compression) and various types of neuritis (nerve inflammation). Increased blood flow from heated tissue promotes tissue healing.
  
  
• Tendinitis. Inflammation of a tendon, a fibrous tissue connecting a muscle with its bony attachment.
  
  
• Bursitis. Inflammation of a bursa, a fluid-filled sac located between a tendon and a bone.
  
  
• Herniated disc. A frequently painful condition in which the cartilage (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.  Direct spine ultrasound is avoided, but painful overlying muscle spasms can be treated.
  
  
• Sprains. A painful wrenching or laceration of the ligaments of a joint.
  
  
• Contusions. Injuries with no sign of broken or ruptured skin, resulting in pain, inflammation and discoloration.
  
  
• Whiplash. An injury to the neck resulting from a sudden jerking of the head.
  
  
• Rotator cuff injury. The rotator cuff is composed of the muscles and tendons that connect the upper arm bone (humerus) to the shoulder blade (scapula). Tendons in the rotator cuff are normally strong, but they can become inflamed and tear as a result of athletic injury, overuse, age-related wear and tear or an accident resulting in trauma (e.g., a collision).
  
  
• Frozen shoulder (adhesive capsulitis). Shoulder pain and stiffening due to injury or disease.  Ultrasound is used to increase range of motion.
  
  
• Arthritis. Inflammation of the joints. Types of arthritis that may benefit from ultrasound or other thermotherapy include:
  
• • Osteoarthritis. A rheumatic disease resulting in the progressive deterioration of the joint cartilage (the softer parts of bones, which cushion their connections to each other) and the formation of bone spurs at the margins of the joints.
    
    

    

  • Rheumatoid arthritis. A long-term inflammatory disease that primarily affects the joints and surrounding tissues, but can also affect other organ systems.
    
    
  • Juvenile rheumatoid arthritis. The most common type of arthritis in children, resulting in damage, stiffness and change in the growth of joints.
    
    
  • Ankylosing spondylitis. An inflammatory disease that affects the joints between the vertebrae of the spine, and the joints between the spine and the pelvis. It eventually causes the affected vertebrae to fuse or grow together.
    
    
  • Gout. One of the most painful types of arthritis, caused by the buildup of uric acid in the body.
    
    
  • Psoriatic arthritis. A form of arthritis resulting in a chronic rash and joint inflammation, among other symptoms.
    
    
  • Reiter’s syndrome. A type of arthritis which causes inflammation of the urethra and lining of the eyes as well as lesions of the skin and mucous membranes.
    
    
• Myofascial pain syndrome. A chronic disorder characterized by pain and tenderness due to localized muscle spasms, known as trigger points.
  
  
• Fibromyalgia. A rheumatic condition characterized by widespread muscle pain, fatigue and poor sleep.
  
  
• Systemic lupus erythematosus. An autoimmune disease that affects the joints, skin and other areas of the body.
  
  
• TMJ disorder. A group of symptoms that often include pain in the jaw's temporomandibular joints, headaches, earaches, restricted jaw movement, clicking or popping sounds as the jaw moves, and may include neck pain, back pain or shoulder pain.
  
  
• Complex regional pain syndrome. A condition involving persistent pain in a limb, thought to be due to an overactive sympathetic nervous system. It may occur after an injury.
  
  
• Carpal tunnel syndrome. Pain or numbness caused by compression of the median nerve in the wrist. Some research has found that ultrasound may be effective for this type of wrist pain.
  
  
• Other types of joint pain.
  
  
• Phantom limb pain. Pain in a limb that persists after amputation of that limb.
  
  
• Wound care. Physical therapists sometimes use ultrasound to promote healing of chronic wounds such as diabetic foot ulcers.  The increase in blood flow from heated tissues promotes healing.

Patients experiencing chronic musculoskeletal pain may receive a referral from a physician for ultrasound therapy performed by a physical therapist or occupational therapist. Others who may offer ultrasound therapy include athletic trainers, practitioners of manipulation therapy such as chiropractors, and (less commonly) speech language pathologists, who may use it for certain types of swallowing problems (dysphagia).

Before administering this form of thermotherapy or diathermy, the practitioner will likely obtain a medical history and conduct a physical examination or similar evaluation, as thermotherapy is recommended for particular conditions.

Patients may be asked to describe the pain in detail. They may also be given a pain assessment, such as a diagram of the body and asked to mark areas where they are experiencing pain. Questions to assess the pain may include:

• Can you describe the pain?
• Where does the pain occur?
• How long have you experienced the pain?
• Have you experienced this type of pain in the past?
• Is the pain constant, or does it come and go?
• Are there any movements that make the pain worse?
• Do you have limited movement?
• Have you ever had thermotherapy for the same condition or any other disorder?

In some cases ultrasound therapy may be used after other modalities, such as a hot pack, cold pack (cryotherapy) or electrical therapy.

Depending on the area being treated, the patient may sit in a chair or lie on a padded table during the procedure. Articles of clothing and jewelry may need to be removed. Sometimes it is necessary for patients to change into a hospital gown.

The therapist will cleanse the area to be treated and apply a coupling agent, such as an ultrasound gel, to provide effective conduction between the ultrasound head (transducer) and the skin. Sometimes a physician prescribes phonophoresis, the use of ultrasound to introduce topical medications (such as a corticosteroid, analgesic or anesthetic) through the skin.

The frequency, intensity and duration of treatment depend on the individual condition. The practitioner will place the head of the ultrasound machine on the area being treated and move it in small circular motions. The ultrasound head must be moved continuously over the treatment site to avoid hot spots and burns.

The transducer should not be placed over a draining wound or the eyes, skull, spinal cord (which may be exposed after some types of spinal surgery), heart, reproductive organs or a pacemaker or other active implanted device. Depending on instructions from the physician, in some cases it may be used with caution near static metal implants such as a joint replacement (arthroplasty). Direct spinal application of ultrasound is also avoided in people who have had back surgery.

The ultrasound waves can be applied in two modes: continuous or pulsed. During continuous mode, the beam of ultrasound the patient receives is constant. With pulsed mode, the waves are transmitted in short or intermittent transmissions that prevent the tissues from heating but still provide mechanical effects such as greater permeability of cell walls.

During the procedure, the patient should experience a comfortable heating or no sensation at all. Treatment time varies according to the injury or condition, but usually lasts between five and 10 minutes.

Afterward, the patient may resume daily activities according to the therapist’s or physician’s orders. The procedure is often followed by exercise therapy or practice with activities of daily living (ADLs) to increase the patient’s range of motion and function.

As with most forms of physical or occupational therapy, patients have numerous visits over a period of time. Duration of treatment depends on the condition being treated as well as the treatment plan outlined by the therapist. Progress may be tracked with assessment tools such as a pain scale or a goniometer, a protractor-like device that measures joints’ range of motion.

Ultrasound therapy is generally safe for most people. However, if used improperly or by a person not experience in its application, it may cause burns or unstable cavitation (collapse of gas bubbles in tissue, which may cause damage).

This type of thermotherapy or diathermy is not recommended in some instances, such as:

• Over the skull, eyes, heart, reproductive organs and bony prominences
  
  
• Over the abdomen of a pregnant woman
  
  
• Over infections or oozing wounds
  
  
• Near tumors
  
  
• Near areas of bone overgrowth, such as from Paget’s disease
  
  
• Over growing bones of children
  
  
• Near an exposed spinal cord, such as after a laminectomy
  
  
• Near pacemakers or other active implanted devices
  
  
• Near static metallic implants such as joint replacements, unless approved by the patient’s physician
  
  
• With patients whose sensation is impaired by conditions such as diabetic neuropathy

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 ultrasound therapy:

1. How can ultrasound therapy help alleviate my pain?
   
   
2. Is ultrasound therapy safe for me? Does it pose any risks for me? Do I have, or am I at risk of, any conditions for which ultrasound therapy is not recommended?
   
   
3. How often and for how long will I have to undergo the treatment?
   
   
4. Where do you recommend I have my ultrasound therapy?
   
   
5. Which type of health professional will perform my treatment?
   
   
6. What will my initial evaluation include?
   
   
7. Will I receive continuous ultrasound to provide thermotherapy, or pulsed ultrasound to produce other effects?
   
   
8. Should I feel any heat or discomfort during the session?
   
   
9. Will my ultrasound sessions be followed by exercise therapy or other activities?
   
   
10. How will my progress be recorded?
    
    
11. Will I also need to undergo other types of physical therapy, occupational therapy or manipulation therapy for my condition?
    
    
12. Are there any lifestyle modifications I need to make when undergoing ultrasound therapy?