Ultrasound Treatment for Osteoarthitis

Assessing the Benefits of Ultrasound Therapy

A physical therapist performs an ultrasound on a patient’s knee.
A physical therapist performs an ultrasound on a patient’s knee.. Hero Images/Getty Images

Therapeutic ultrasound is an option in physical therapy to treat pain and loss of joint function due to osteoarthritis. Typically, therapeutic ultrasound is performed in a physical therapy clinic, or sometimes a doctor's office. Although it is a treatment option for osteoarthritis, its effectiveness is still questioned.

What Is Therapeutic Ultrasound?

Therapeutic ultrasound utilizes sound waves which cause vibration to decrease pain or improve joint function.

The vibrations may be pulsed or continuous. Continuous ultrasound vibrations generate noticeable heat, while pulsed ultrasound vibrations do not. The vibrations occur at high frequency — so high that the vibrations would be undetectable to the patient.

How Does Therapeutic Ultrasound Work?

In 1987, a researcher (Dyson) proposed that for therapeutic ultrasound to achieve beneficial effects, tissue must reach a temperature of 40°C to 45°C for at least 5 minutes. More recently, other researchers (Draper et al) studied thermal effects (i.e., increase in tissue temperature) when treated with 1-MHz or 3-MHz ultrasound. Prior to these studies, the frequency and duration of ultrasound treatment was purely estimated.

Researchers (Lennart D. Johns, et al.) also considered non-thermal effects of ultrasound in an effort to study just the mechanical effects of ultrasound. Non-thermal effects of therapeutic ultrasound include acoustic streaming and cavitation.

According to Johns, acoustic streaming is defined as "the physical forces of the sound waves that provide a driving force capable of displacing ions and small molecules." Cavitation is defined as "the physical forces of the sound waves on microenvironmental gases within fluid." These effects occur at the cellular level, likely causing injury to the cell.

To simplify what occurs next, let us assume that it is akin to what typically occurs after any tissue injury: healing of the tissue which begins with a phase of acute inflammation.

Effectiveness of Therapeutic Ultrasound

In 2008, a study was published in the Journal of the Canadian Chiropractic Association that reviewed conclusions from experimental, clinical, and animal studies of therapeutic ultrasound for osteoarthritis. Using a PubMed search starting in the year 1985, researchers found 16 studies that met their criteria for inclusion in the review. There were 9 studies that concluded therapeutic ultrasound has beneficial effects on pain and function. Five studies suggested that ultrasound had cartilage healing properties. One experimental study showed increased absorption of hyaluronan using ultrasound phonophoresis. There was just one study that concluded there was no effect on pain or range of motion when ultrasound treatment was combined with exercise. Also, of 5 review papers, two concluded there were positive effects from therapeutic ultrasound, two did not find any benefit, and one was inconclusive.

In 2010, a Cochrane review of studies utilizing therapeutic ultrasound for knee and hip osteoarthritis was performed. The review evaluated studies that compared ultrasound to sham or no intervention for pain and function. Five small trials, involving a total of 341 patients with knee osteoarthritis, were included in the Cochrane review. Two of the 5 evaluated pulsed ultrasound, two evaluated continuous ultrasound, and one evaluated a combination of pulsed and continuous ultrasound. Reviewers concluded that ultrasound may be beneficial for osteoarthritis of the knee. But, they were uncertain about how significant the beneficial effects were on pain and function and felt there was a need for better designed studies.

Yet another study, published in 2011 in the journal Orthopaedic Surgery, concluded that ultrasound significantly relieved joint symptoms and joint swelling, while improving joint mobility and reducing inflammation in people with osteoarthritis. The study involved 87 patients with knee osteoarthritis who received ultrasound treatment for 9 months (from February to October 2010).


Mechanisms involved in therapeutic ultrasound. Dyson M. Physiotherapy. 1987;73:116–120.

Rate of temperature increase in human muscle during 1 MHz and 3 MHz continuous ultrasound. Draper DO et al. J Orthop Sports Phys Ther. 1995 Oct;22(4):142-50.

Nonthermal Effects of Therapeutic Ultrasound: The Frequency Resonance Hypothesis. Lennart D. Johns. Journal of Athletic Training. 2002 Jul-Sep; 37(3): 293–299.

Ultrasound in the management of osteoarthritis: part I: a review of the current literature. Srbely JZ DC, PhD. March 2008.

Therapeutic ultrasound for osteoarthritis of the knee or hip. Cochrane Database Systematic Review. 2010 Jan 20;(1):CD003132. doi: 10.1002/14651858.CD003132.pub2.

Efficacy of ultrasound in the treatment of osteoarthritis of the knee. Yang P-f. et al. Orthopaedic Surgery. August 2011.

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