Therapeutic Ultrasound in Physical Therapy

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

Ultrasound in physical therapy is different than diagnostic ultrasound. With the latter, healthcare providers use ultrasound to see the inside of the body. For example, diagnostic ultrasound lets healthcare providers check on a fetus during pregnancy.

This article explains how therapeutic ultrasound works and when it's used.

Therapeutic ultrasound
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What Is Therapeutic Ultrasound?

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

Deep Heating Effects

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

  • Increase circulation to tissues
  • Speed the healing process
  • Decrease pain
  • Increase elasticity

Deep heating can increase the "stretchiness" of muscles and tendons that may be tight.

If you have shoulder pain and have been diagnosed with a frozen shoulder, your physical therapist (PT) may use ultrasound. This therapy is usually done before performing range of motion exercises because it can help improve the ability of your shoulder to stretch.

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Click Play to Learn More About the Use of Therapeutic Ultrasound

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

Non-Thermal Effects (Cavitation)

In addition to heat, ultrasound introduces energy into the body. This energy causes microscopic gas bubbles around your tissues to expand and contract rapidly, a process called cavitation.

It is theorized that the expansion and contraction of these bubbles help speed cellular processes and help injured tissue heal faster.

When cavitation is unstable, it can be dangerous to your body's tissues. So, your physical therapist will work to ensure that the cavitation during therapy is stable.

Recap

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

How Does Ultrasound Work?

Inside your physical therapist's ultrasound unit is a small crystal. When an electrical charge hits this crystal, it vibrates rapidly, creating piezoelectric waves (an electric charge that accumulates in some solid materials). These waves emit from the ultrasound sound head as ultrasound waves.

During treatment, the ultrasound wave then enters into your injured tissues. This exposure to ultrasonic waves increases blood flow and cavitation, leading to the theorized benefits of the treatment.

When Is It Used?

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

Injuries

Usually, PTs treat orthopedic (musculoskeletal) injuries with ultrasound. These may include:

  • Bursitis (inflammation in the fluid-filled sacs along joints)
  • Tendonitis
  • Muscle strains and tears
  • Frozen shoulder
  • Sprains and ligament injuries
  • Joint contracture or tightness

Generally speaking, any soft-tissue injury in the body may be a candidate for ultrasound therapy. For example, your physical therapist may use ultrasound for low back pain, neck pain, rotator cuff tears, knee meniscus tears, or ankle sprains.

Chronic Pain

There is also some evidence that you may benefit from ultrasound treatments if you have chronic pain. It is thought that the ultrasound waves help improve tissue extensibility and circulation, leading to increased mobility and, ultimately, decreased pain.

Recap

PTs use therapeutic ultrasound for specific soft-tissue injuries, including joint pain, muscle strains and tears, and ligament injuries. In addition, they sometimes use it for chronic pain.

What to Expect

Ultrasound uses a machine that has an ultrasound transducer (sound head). First, a PT applies a small amount of gel to the particular body part; then, your physical therapist slowly moves the sound head in a small circular direction on your body.

What Ultrasound Feels Like

While receiving an ultrasound treatment, you will most likely not feel anything happening, except perhaps a slight warming sensation or tingling around the treatment area.

If the ultrasound sound head is left in place on your skin and not moved in a circular direction, you may experience pain. If this occurs, tell your physical therapist right away.

Settings

The therapist may change various settings of the ultrasound unit to control the ultrasound wave's penetration depth or change the ultrasound's intensity. In addition, they may use different settings during various stages of healing.

Methods

Alternative methods of ultrasound application are available if the body part is bony and bumpy or if there's an open wound. (The ultrasound gel and sound head may harbor bacteria that can enter the wound.) These include:

  • Direct contact (most commonly used method)
  • Water immersion
  • Bladder technique

Ultrasound + Medication

Your PT may use ultrasound gel combined with a topical medication to help treat inflammation around the soft tissue in the body. This process is called phonophoresis.

While there is evidence that ultrasound waves help deliver the medicated gel to the injured tissues, most published studies indicate that this treatment may be ineffective.

Recap

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

Contraindications

There are some instances where you should not use ultrasound at all. These contraindications to ultrasound may include:

  • Over open wounds
  • Over metastatic lesions (cancer that has spread) or any active areas of cancer
  • Over areas of decreased sensation
  • Over parts of the body with metal implants, like in a total knee replacement or lumbar fusion
  • Near or over a pacemaker
  • Pregnancy
  • Around the eyes, breasts, or sexual organs
  • Over fractured bones
  • Near or over an implanted electrical stimulation device
  • Overactive epiphyses in children
  • Over an area of acute infection

Does Evidence Support Its Use?

Many studies have found that ultrasound offers little benefit to the overall outcome of physical therapy. In fact, in a series of papers published in Physical Therapy Journal in 2001, ultrasound received a grade of "C" (no benefit demonstrated) for certain conditions, including:

  • Knee pain
  • Low back pain
  • Neck pain

In addition, a 2014 study in the American Journal of Physical Medicine and Rehabilitation examined the effect of ultrasound on pain and function in patients with knee osteoarthritis. The researchers found no difference in knee function and pain with rehab using ultrasound, no ultrasound, and sham (fake) ultrasound.

Is It Right For You?

Some argue that ultrasound can harm your physical therapy by needlessly prolonging your care. So, if your physical therapist is providing ultrasound for you, you may question if it is really necessary as part of your overall rehab program.

Ultrasound may not work for everyone, but it may be worth a try if you have chronic, ongoing pain. Some people may suggest that the benefit of ultrasound for chronic pain is due to the placebo effect. But, if it gives you relief, then it is the proper treatment for you.

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

Exercise and active involvement should always be the main components of your rehab program.

Summary

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

A Word From Verywell

If your physical therapist suggests ultrasound, be sure to ask about why it's needed and possible risks. Also, be sure to perform an active self-care exercise program in the PT clinic and at home. If you are actively engaged in your rehabilitation, you can ensure that you have a safe and rapid recovery back to normal function.

Frequently Asked Questions

  • Why is ultrasound used in physical therapy?

    Therapeutic ultrasound is used in physical therapy to help heal soft tissue like muscles, tendons, and ligaments. Ultrasound technology involves applying electricity to a special crystal. This process creates piezoelectric waves that emit from the ultrasound wand. The waves deep heat the soft tissue, increasing blood flow to the area to promote healing. 

  • What does therapeutic ultrasound feel like?

    You typically won’t feel much during ultrasound therapy. The physical therapist will apply a gel then rub the wand against the skin in the area of the injury. You may start to feel a warm sensation, or you may not feel anything at all. Tell your PT if you experience any discomfort during the treatment.

  • Does therapeutic ultrasound help relieve pain?

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

  • Is therapeutic ultrasound safe?

    Yes, therapeutic ultrasound is a safe, FDA-approved treatment. There are no known harmful side effects from a therapeutic ultrasound performed correctly by a physical therapist.

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4 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Jia L, Wang Y, Chen J, Chen W. Efficacy of focused low-intensity pulsed ultrasound therapy for the management of knee osteoarthritis: a randomized, double blind, placebo-controlled trial. Sci Rep. 2016;6:35453. doi: 10.1038/srep35453

  2. Yeğin T, Altan L, Kasapoğlu Aksoy M. The effect of therapeutic ultrasound on pain and physical function in patients with knee osteoarthritis. Ultrasound Med Biol. 2017;43(1):187-194. doi:10.1016/j.ultrasmedbio.2016.08.035

  3. Albright J, et al. Philadelphia panel evidence-based clinical practice guidelines on selected rehabilitation interventions for low back pain. Physical Therapy. 2001;81(10):1641-1674. doi:10.1093/ptj/81.10.1641

  4. Cakir S, Hepguler S, Ozturk C, Korkmaz M, Isleten B, Atamaz FC. Efficacy of therapeutic ultrasound for the management of knee osteoarthritis: a randomized, controlled, and double-blind study. Am J Phys Med Rehabil. 2014;93(5):405-12. doi:10.1097/PHM.0000000000000033