therapeutic ultrasound
The same kind of sound used to make pictures of a baby in the womb can also be used, at higher intensity, as a treatment. Therapeutic ultrasound is a small handheld device that sends high-frequency sound waves, far above what the ear can hear, into the body to warm or mechanically stimulate deep tissue.
A clinician spreads a gel on the skin (because sound does not travel from air into tissue well) and slowly moves the round sound head over the area. The sound waves penetrate three to five centimetres and do two things, depending on the settings. On a continuous setting they create heat deep in the tissue — a deep heating agent that can warm a tendon or joint capsule to make it more stretchable. On a pulsed setting the heating is minimal and the so-called nonthermal effects dominate: the rapid vibration causes tiny gas bubbles in the tissue fluid to oscillate, a phenomenon called cavitation, which is thought to gently agitate cells and may influence healing.
Therapeutic ultrasound is one of the most widely used modalities, often applied for tendon problems, scar tissue, and trigger points. It is also one of the most honestly debated: high-quality trials show its benefit for many common conditions is small, inconsistent, or no better than a switched-off (placebo) device. It is reasonable as part of a programme built mainly around exercise, but it should not be the centrepiece. It is avoided over the eyes, over a pregnant uterus, over tumours, over the heart and over pacemakers, and over growth plates in children.
A therapist uses continuous ultrasound over a stiff, scarred Achilles tendon to warm it deeply, then immediately has the patient stretch — but treats the ultrasound as a warm-up, with daily loading exercise as the real treatment.
A popular modality whose proven benefit is modest — keep it as an adjunct.
Despite being everywhere in clinics, high-quality trials often show therapeutic ultrasound is no better than a switched-off sham device for many conditions.