Ultrasound treatments have been around since the 1950s. They are most often used by physical therapists or occupational therapists to treat pain conditions and to promote tissue healing. While ultrasound therapy is not effective for all chronic pain conditions, it may help reduce your pain if you have osteoarthritis.
The ultrasound unit gets its power from the electricity in the wall outlet. The electricity enters the unit at the standard 60 cycles per second (60 Hertz). The ultrasound machine ramps the frequency up much higher, generally either to one million (one megahertz, or 1 MHz) or 3.5 million (3.5 MHz) cycles per second. The electricity then travels through an insulated cord to the handle. The electricity is passed through a special crystal inside the transducer, the part placed on your body. The electrical current vibrates the crystal to produce sound waves at the same frequency. These sound waves enter your body through the transducer.
The 1 MHz setting sends waves over a deeper and wider area. It is used to reach tissues up to two inches below the skin surface–deeper tissues of the spine, for example. The 3.5 MHz setting creates waves that are packed more closely together. It is used to treat tissues just under the surface of the skin, such as the jaw, tendons of the hands and feet, or bony areas around the elbow.
Ultrasound treatments are used to ease pain, improve circulation, and speed healing. Ultrasound treatments can be manipulated to have different effects. Your therapist can set the frequency and intensity of the sound waves to create heat in the sore area. This thermal effect brings in blood to the sore area. The blood brings in oxygen and nutrients, and it flushes away waste products and chemicals that may be causing pain. Thermal treatments can also stimulate the nerve sensors to start easing pain. As the pain eases, tight muscles can relax, which further relieves the cycle of pain.
The ultrasound machine can also be set in a way that avoids a thermal effect. This is often necessary if the area is swollen or severely inflamed. The non-thermal treatments can help move body chemicals to and from the cells in the sore area. This can help speed the healing process.