What does US diathermy accomplish?

• A. cools tissue
• B. causes muscle contraction
• C. provides superficial heating only
• D. increases molecular movement, leading to a deep heat within tissue (muscles, tendons, and joints) to reduce pain, muscle spasms, and joint stiffness

Answer: (D)

Ultrasound diathermy works by converting sound energy into heat inside the tissues. This energy penetrates beyond the surface, especially at lower frequencies, producing deep heating in muscles, tendons, and joints. The temperature rise increases molecular movement, enhances blood flow and metabolic activity, and helps relax tight muscles, reduce pain, and improve joint flexibility. It’s this deep, sustained heating effect that makes it effective for easing stiffness and spasms, rather than cooling tissue, causing contraction, or limiting heating to the superficial layers.