Therapeutic ultrasound is used in physical therapy to treat pain and loss of joint function due to osteoarthritis. Osteoarthritis occurs when cartilage in the joints breaks down over time. Also known as wear-and-tear arthritis, degenerative joint disease, and degenerative arthritis, osteoarthritis causes joint pain and stiffness that can interfere with everyday activities. This article discusses how ultrasound therapy works and how it can help treat osteoarthritis in the hip and knee. It also looks at the effectiveness of therapeutic ultrasound on knee and hip pain.

What Is Therapeutic Ultrasound?

Therapeutic ultrasound is a passive therapy used in physical therapy clinics to treat osteoarthritis. The ultrasound machine contains a crystal that produces ultrasonic waves upon receiving an electrical charge.

These high-frequency sound waves create tiny vibrations that are able to pass in through your skin to reach deeper tissues. These vibrations are virtually undetectable to the person receiving ultrasound treatment. They are also too high a frequency to be heard by human ears.

Ultrasound vibrations can be delivered as pulses or continuous waves. Continuous ultrasound vibrations generate noticeable heat, while pulsed ultrasound vibrations do not. It’s thought that both thermal and non-thermal effects are responsible for any effects these treatments may have.

How Therapeutic Ultrasound Works for Arthritis

Ultrasound works to treat osteoarthritis and other soft tissue damage using either thermal or non-thermal effects.

Therapeutic ultrasound is different than diagnostic ultrasound. Diagnostic ultrasound is used to create images of internal structures and is used to diagnose an injury or disease or manage pregnancy. Therapeutic ultrasound does not take images. It has been used as a treatment since 1950.

Ultrasound waves are able to penetrate deep tissue reaching internal structures that other external heat sources (like a heating pad) can’t touch. To be effective, therapeutic ultrasound needs to heat the tissue between 104°F to 113°F for at least 5 minutes.

Ultrasound is also thought to improve cellular function by making microscopic gas bubbles near your injury expand and contract rapidly, a process called cavitation. This expansion and contraction are thought to speed up the healing process in your injured body part.

Effectiveness for Knee and Hip Arthritis

Studies evaluating the effectiveness of therapeutic ultrasound on osteoarthritis have been mixed; some studies found no benefit, and others found some benefits.

A 2019 review of 15 studies with 1,074 patients found therapeutic ultrasound is a safe and effective treatment for osteoarthritis in the knee. The studies show it helps to relieve pain and improve the physical function of the knee. 

A 2021 meta-analysis of 14 studies including 1,080 people with knee osteoarthritis found both pulsed and continuous ultrasound are effective and safe for pain relief and functional recovery.

Another study found that low-energy pulsed ultrasound provided about four weeks of pain reduction and improved functioning and quality of life.

Side Effects of Therapeutic Ultrasound

When appropriately performed by a medical professional, therapeutic ultrasound is a safe therapy with virtually no side effects. The treatment uses a hypoallergenic gel that should not cause skin irritation. 

The healthcare provider will slowly move the ultrasound wand in a circular motion over the area during the treatment. If the transducer is left in one place for too long, it can cause a superficial skin burn, similar to a sunburn.

A Word From Verywell

Therapeutic ultrasound is a non-invasive treatment that may be effective in treating osteoarthritis in the knee and hip. The therapy appears to be very safe, has few adverse effects, and is relatively inexpensive. There is a wide range of osteoarthritis treatments available. Talk to your healthcare provider to find out if ultrasound therapy for osteoarthritis is right for you.

Frequently Asked Questions

  • Is therapeutic ultrasound painful?
  • No, the sound waves used in ultrasound therapy only create tiny vibrations. You won’t feel them or hear the frequencies, but you may feel warmth.
  • Does therapeutic ultrasound reduce inflammation?
  • Yes, research shows that therapeutic ultrasound reduces tissue inflammation in people with osteoarthritis in the hip or knee. One study found that it mitigates inflammation and facilitates tissue repair.
  • Are there any therapeutic ultrasound contraindications?
  • Therapeutic ultrasound should not be used in people with cancer, children, or pregnant people. It also cannot be used on certain areas in those with decreased sensitivity or total joint replacements.
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  • Is Therapeutic Ultrasound Safe For My Condition?

No, the sound waves used in ultrasound therapy only create tiny vibrations. You won’t feel them or hear the frequencies, but you may feel warmth.

Yes, research shows that therapeutic ultrasound reduces tissue inflammation in people with osteoarthritis in the hip or knee. One study found that it mitigates inflammation and facilitates tissue repair.

Therapeutic ultrasound should not be used in people with cancer, children, or pregnant people. It also cannot be used on certain areas in those with decreased sensitivity or total joint replacements.