Diathermy refers to the application of which of the following?

• A. Cryotherapy to cool tissue
• B. Shortwave or microwave electromagnetic energy to produce heat within tissues
• C. Electrical stimulation of nerves
• D. Ultrasound to heat tissue

Answer: (B)

Diathermy involves heating tissue with high-frequency electromagnetic energy. It uses shortwave or microwave energy to raise the temperature inside tissues, producing deeper heating than many other thermal modalities. The energy is nonionizing and works through dielectric heating mechanisms: capacitive methods place an electric field across tissues, heating those with higher impedance, while inductive methods use a changing magnetic field to induce currents inside the tissues, generating heat. This deeper heating can improve tissue extensibility, increase blood flow, and help with pain and stiffness.

This is different from cryotherapy, which cools tissue to reduce inflammation; electrical stimulation targets nerves or muscles with electrical currents without primarily heating tissue; and ultrasound heats tissue via acoustic energy. The defining feature of diathermy is the use of shortwave or microwave electromagnetic energy to produce heat within the body.