Sound wave generation: A therapeutic ultrasound machine generates high-frequency sound waves using a piezoelectric crystal within the ultrasound transducer. When an electric current passes through the crystal, it vibrates rapidly, producing sound waves.

Transmission through tissue: The sound waves generated by the ultrasound machine are applied to the skin through a handheld transducer head. Before application, a coupling gel is typically applied to the skin to help transmit the sound waves and reduce friction.

Absorption and reflection: Once the sound waves penetrate the skin, they encounter different types of tissues, including muscles, tendons, ligaments, and bones. These tissues have different densities and compositions, which affect how the sound waves are absorbed and reflected.

Biological effects: As the sound waves travel through the tissues, they cause mechanical vibrations at a cellular level. These vibrations can lead to several biological effects:

• Thermal effects: The rapid vibration of molecules within the tissues generates heat. This increase in tissue temperature can promote relaxation of muscles, improve blood flow, and enhance tissue healing.

• Micro-massage: The mechanical vibrations produced by the sound waves create micro-streaming within the tissues, which can help facilitate the movement of fluids and cellular substances. This micro-massage effect can aid in reducing inflammation and promoting tissue repair.

• Increased cell membrane permeability: The oscillation of cells induced by ultrasound can temporarily increase the permeability of cell membranes. This can enhance the uptake of nutrients and the removal of metabolic waste products, contributing to tissue healing.

• Stimulation of biological processes: Ultrasound has been shown to stimulate various cellular processes, including collagen synthesis, fibroblast proliferation, and angiogenesis (the formation of new blood vessels). These processes are essential for tissue repair and regeneration.