Therapeutic Ultrasound in Physical Therapy

Therapeutic ultrasound is a treatment commonly used in physical therapy that provides deep heating of soft tissues in the body. These tissues include muscles, tendons, joints, and ligaments.

Ultrasound in physical therapy is different from diagnostic ultrasound. For the latter, healthcare providers use ultrasound to look inside the body. For example, a diagnostic ultrasound can allow health care providers to examine the fetus during pregnancy.

This article explains how therapeutic ultrasound works and when to use it.

What is therapeutic ultrasound?

Therapeutic ultrasound is used to heat tissue and introduce energy into the body.

Deep heating effect

Ultrasound can provide deep heating of soft tissue structures in the body. Deep heating of tendons, muscles, or ligaments may have the following benefits:

  • Increase circulation in the organization
  • Speed ​​up the healing process
  • pain relief
  • increase flexibility

Deep heating can increase the “elasticity” of muscles and tendons that may be tight.

If you have shoulder pain and have been diagnosed with frozen shoulder, your physical therapist (PT) may use an ultrasound. This therapy is usually done before range-of-motion exercises, as it can help improve shoulder extension.

This video has been medically reviewed by Laura Campedelli (PT, DPT).

Non-thermal effects (cavitation)

In addition to heat, ultrasound also introduces energy into the body. This energy causes tiny air bubbles around the tissue to rapidly expand and contract, a process called cavitation.

In theory, the expansion and contraction of these bubbles helps speed up cellular processes and helps injured tissue heal faster.

When cavitation is unstable, it can be dangerous to your body tissues. Therefore, your physical therapist will work to ensure that cavitation is stable during treatment.


Therapeutic ultrasound uses heat and energy to increase circulation, reduce pain, increase flexibility, and speed healing.

How does ultrasound work?

Inside your physical therapist’s ultrasound unit is a small crystal.When an electric charge hits this crystal, it vibrates rapidly, producing Piezoelectric Waves (electric charges that build up in certain solid materials). These waves are emitted from the ultrasound probe as ultrasonic waves.

During treatment, ultrasound waves are passed into your injured tissue. This exposure to ultrasound increases blood flow and cavitation, resulting in theoretical therapeutic benefits.

When is it used?

PT may use therapeutic ultrasound to treat some injuries and chronic pain.


Typically, PT uses ultrasound to treat orthopedic (musculoskeletal) injuries. These may include:

  • Bursitis (inflammation in the fluid-filled sac along the joint)
  • tendonitis
  • Muscle strains and tears
  • frozen shoulder
  • Sprains and Ligament Injuries
  • joint contractures or tightness

In general, any soft tissue injury in the body may be a candidate for ultrasound therapy. For example, your physical therapist may use ultrasound to treat low back pain, neck pain, a torn rotator cuff, a torn meniscus in your knee, or a sprained ankle.

chronic pain

There is also some evidence that if you have chronic pain, you may benefit from ultrasound therapy. Ultrasound is thought to help improve tissue extensibility and circulation, thereby increasing mobility and ultimately reducing pain.


PT uses ultrasound to treat specific soft tissue injuries, including joint pain, muscle strains and tears, and ligament injuries. Also, they sometimes use it for chronic pain.

Ultrasound therapy for chronic pain

what to expect

Ultrasound uses a machine with an ultrasonic transducer (sound head). First, the PT applies a small amount of gel to a specific body area; your physical therapist then moves the capsule slowly across your body in a small circular direction.

What does an ultrasound feel like

You most likely won’t feel anything happening while you’re having an ultrasound, except maybe a slight warmth or tingling around the treated area.

You may experience pain if the ultrasound probe remains on your skin and does not move in a circular direction. If this happens, tell your physical therapist right away.

set up

The therapist can change various settings of the ultrasound unit to control the depth of penetration of the ultrasound or change the intensity of the ultrasound. Additionally, they may use different settings during different treatment stages.


If the body part is bony and uneven or has an open wound, other ultrasound applications may be used. (Ultrasonic gels and capsules may contain bacteria that can enter wounds.) These include:

  • Direct contact (the most common method)
  • soaking
  • Bladder Technology

Ultrasound + Drugs

Your PT may use ultrasound gel and topical medications to help treat inflammation around the soft tissues of your body.This process is called Acoustophoresis.

While there is evidence that ultrasound can help deliver the drug gel to injured tissue, most published studies suggest the treatment may not be effective.


Therapeutic ultrasound does not produce many bodily sensations other than the sensation of the ultrasound wand against your skin. Your PT may use different settings or different application methods depending on your situation.


In some cases, you shouldn’t use ultrasound at all. These ultrasound contraindications may include:

  • on open wounds
  • Metastatic lesions (cancer that has spread) or any areas of cancer activity
  • in areas of decreased sensation
  • covering parts of the body with metal implants, such as total knee replacement or lumbar fusion
  • near or over the pacemaker
  • pregnant
  • around the eyes, breasts, or sex organs
  • more than a fractured bone
  • near or above an implantable electrical stimulation device
  • hyperactive Epiphysis in children
  • in an acutely infected area

Is there evidence to support its use?

Many studies have found that ultrasound has little benefit to overall physical therapy outcomes.In fact, in a series published in Journal of Physical Therapy In 2001, ultrasound received a “C” grade (showing no benefit) in certain conditions, including:

  • knee pain
  • low back pain
  • neck pain

Additionally, a 2014 study found American Journal of Physical Medicine and Rehabilitation Examining the effects of ultrasound on pain and function in patients with knee osteoarthritis. The researchers found no difference in knee function and pain when using ultrasound, no ultrasound, and sham (sham) ultrasound for rehabilitation.

Is it right for you?

It has been argued that ultrasound can harm your physical therapy by unnecessarily prolonging your nursing care. Therefore, if your physical therapist gives you an ultrasound, you may question whether it is really necessary as part of your overall rehabilitation program.

Ultrasound may not work for everyone, but it may be worth a try if you have chronic persistent pain. Some may argue that the benefits of ultrasound for chronic pain are due to the placebo effect. But if it gives you relief, then it’s the treatment for you.

Ultrasound is a passive treatment. In other words, you cannot provide the treatment yourself; you are a passive recipient of the ultrasound. If your physical therapist uses ultrasound during your treatment, make sure you participate in an active exercise program to help improve your functional mobility.

Exercise and active participation should always be a major part of your rehabilitation program.


Therapeutic ultrasound is different from diagnostic ultrasound. PTs use it to treat some injuries and chronic pain. Evidence on the alleged benefits of therapeutic ultrasound is mixed. However, since it’s low risk for most people, it may be worth a try, especially if you experience chronic pain.

VigorTip words

If your physical therapist recommends an ultrasound, be sure to ask why it is needed and the possible risks. Also, be sure to have an active self-care exercise program at the PT clinic and at home. If you are actively involved in rehabilitation, you can ensure that you return to normal function safely and quickly.

Frequently Asked Questions

  • Why use ultrasound in physical therapy?

    Therapeutic ultrasound is used in physical therapy to help heal soft tissues such as muscles, tendons, and ligaments. Ultrasonic technology involves applying electrical current to a special crystal. This process generates piezoelectric waves that are emitted from the ultrasonic rod. The waves deeply heat the soft tissue, increasing blood flow to the area to promote healing.

  • What does a therapeutic ultrasound feel like?

    During ultrasound treatment, you usually don’t feel much. The physical therapist will apply the gel and then rub the wand on the skin of the injured area. You may start to feel warm, or you may not feel any at all. Tell your PT if you have any discomfort during treatment.

  • Can therapeutic ultrasound help relieve pain?

    Possible, but only as part of a physical therapy regimen that includes stretching and strengthening exercises. On its own, therapeutic ultrasound has no apparent benefit for knee pain, low back pain, or neck pain.

  • Is Therapeutic Ultrasound Safe?

    Yes, therapeutic ultrasound is a safe, FDA-approved treatment. Therapeutic ultrasound when properly performed by a physical therapist has no known harmful side effects.