Ultrasound: How Does Ultrasound Work

There are two main types of ultrasound – diagnostic and therapeutic. 

When most people think about ultrasound, they think of the ‘the thing you have when you are pregnant’. This is correct! 

If you have had bursitis, for example, your GP or physio may have referred you for an ultrasound.

This is a diagnostic one which looks at the integrity of the muscles and tendons as well as measuring the fluid in the bursa.

Diagnostic ultrasound can also be used when looking at abdominal organs, the pelvic cavity or heart and blood vessels.  

The other type is therapeutic ultrasound. Many physiotherapists use this type of modality in their treatments. 

How Does Therapeutic Ultrasound Work? 

Ultrasound waves are a very high frequency sound wave. 

They are created by the vibration of crystals in the head of the ultrasound probe.

These continuous or intermittent waves pass through the skin and other tissue (e.g fat layers) to the underlying tissues. Most of the time, you as the patient will not be able to feel these vibrations. 


Altering the output of the machine can determine the depth that the ultrasound waves reach. 

There are different settings (frequencies and modes) depending on the depth of the area you want to reach (if its superficial tissue or deep tissue), the size of the tissue (how small or large it is) or how acute or chronic an injury is.

Acute injuries have a different setting compared to a problem or injury that is considered chronic, because the effects on the tissues that your therapist wants to achieve will be different. 

Ultrasonic gel (which is blue, and most of the time cold!) is applied to the skin and the head of the ultrasound probe before the machine is turned on.

The gel allows the ultrasound waves to pass through the skin and into the tissues. This gel not medicated. 

Therapeutic Ultrasound administration may take up to 5 minutes, depending on the area and depth that it is being applied to. 


What Are The Benefits Of Therapeutic Ultrasound?

The ultrasound aims to 

  • Increase blood flow to the area it is affecting
  • Increase the rate of healing in the underlying area
  • Alter the phases of tissue repair
  • Stimulate the activity of anti-inflammatory cells
  • Reduce swelling and chronic inflammation
  • Break down scar tissue
  • Generate a deeper heat
  • Alter the nerve input and reduce the sensitivity in the underlying tissue


What Injuries Or Pains Can Therapeutic Ultrasound Be Used For?

Common areas/injuries that it can benefit include;

Although Therapeutic Ultrasound can be used for a variety of conditions, there are some conditions/areas of the body that it is not safe to use it with.

These include; 

  • Locally over a pregnant tummy
  • Over the eyes, anterior neck, reproductive organs
  • Haemorrhagic conditions 
  • Very poor circulation or sensation
  • Infection or tuberculosis
  • Malignancy (cancer)
  • Over recently radiated tissue
  • Over plastic or ceramic implants

Your physiotherapist should ask you if you have any of these contraindications, but be sure to be up front with any medical conditions you have.

Over recent years, there has been conflicting evidence on the benefits of ultrasound, however speak with your physiotherapist and they will help you decide whether it will benefit your specific condition.

It should always be used as an adjunct to treatment, along with active management strategies. 

If you think you would benefit from Ultrasound treatment, get in touch with your physiotherapist. 

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