Therapeutic ultrasound is a treatment modality commonly used in physical therapy. It is used to provide deep heating to soft tissues in the body. These include muscles, tendons, joints and ligaments. Ultrasound in physical therapy is not to be confused with diagnostic ultrasound, which is ultrasound that is used to see the inside of the body, such as checking on a fetus during pregnancy.
What Does Ultrasound Do?
Deep heating effects. Ultrasound is often used to provide deep heating to soft tissue structures in the body. Deep heating tendons, muscles or ligaments increases circulation to those tissues, which is thought to help the healing process. Increasing tissue temperature with ultrasound is also used to help decrease pain.
Deep heating can be used to 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 may use ultrasound to help improve the extensibility of the tissues around your shoulder prior to performing range of motion exercises. This may help improve the ability of your shoulder to stretch.
Non-thermal effects (cavitation). 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 improves healing of injured tissue.
Two types of cavitation include stable and unstable cavitation. Stable cavitation is desired when your physical therapist is applying ultrasound to your body. Unstable cavitation can be dangerous to your body's tissues, and your physical therapist will ensure that this does not occur during the application of ultrasound.
How Is Ultrasound Applied?
Ultrasound is performed with machine that has an ultrasound transducer (sound head). A small amount of gel is applied to the particular body part; then your physical therapist slowly moves the sound head in a small circular direction on your body. The therapist may change various settings on the ultrasound unit to control the depth of penetration of the ultrasound waves or change the intensity of the ultrasound. Different settings are used in various stages of healing.
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.)
Your physical therapist may use ultrasound gel combined with a topical medication to help treat inflammation around soft tissue in the body. This process is called phonophoresis. While there is some evidence that ultrasound waves help deliver the medicated gel to the injured tissues, most published studies indicate that this treatment may be ineffective.
What Does Ultrasound Feel Like?
While you are receiving an ultrasound treatment, you will most likely not feel anything happening, except perhaps a slight warming sensation or tingling around the area being treated. 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.
Common Injuries Treated with Ultrasound
- Muscle strains and tears
- Frozen shoulder
- Sprains and ligament injuries
- Joint contracture or tightness
Caution During Ultrasound
If you are going for physical therapy and are getting ultrasound, you should know that many studies have found that ultrasound offers little benefit to the overall outcome in physical therapy. For example, if you have low back pain, ultrasound treatments have been shown to offer very little benefit. In fact, ultrasound received a grade of "C" (no benefit demonstrated) for knee pain, low back pain and neck pain in a series of papers published in Physical Therapy Journal in 2001. The evidence leads many to wonder if ultrasound really helps you in physical therapy.
Many people argue that ultrasound can have a negative effect on your physical therapy by needlessly prolonging your care. Ultrasound is a passive treatment. In other words, you can't provide the treatment yourself.
Your physical therapist may use ultrasound to help improve your condition. If so, be sure to ask about the need for ultrasound. Also, be sure that you are also performing an active self-care exercise program 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.
Albright, J. et al. Philadelphia panel evidence-based clinical practice guidelines on selected rehabilitation interventions for low back pain. Physical Therapy. 2001. Oct; 81(10): 1641-1674.
Albright, J. et al. Philadelphia panel evidence-based clinical practice guidelines on selected rehabilitation interventions for neck pain. Physical Therapy. 2001. Oct; 81(10): 1701-1717.
Albright, J. et al. Philadelphia panel evidence-based clinical practice guidelines on selected rehabilitation interventions for knee pain. Physical Therapy. 2001. Oct; 81(10): 1675-1700.
Prentice, W. (1998). Therapeutic modalities for allied health professionals. New York: McGraw-Hill.