Focused shockwave therapy uses acoustic waves to produce effects in tissues. For clinicians and patients alike, understanding the physics behind this technology is key to understanding how it works. This post breaks down the core principles of shockwave physics from wave propagation to the different types of devices used in clinical practice.
A shockwave is not a continuous wave but a single powerful acoustic pulse. Its journey and characteristics can be broken down into several stages.
It all starts with the Wave Front, which is the leading edge of the shockwave. This front rises to its maximum pressure in no time. The time it takes to get there is called the Rise Time. Immediately after that the pressure starts to fall.
The entire time from the initial rise to the return to zero pressure is called the Positive Pressure Phase. Then the wave enters the Negative Pressure Phase where it dips below baseline before returning to zero, completing the cycle. All of this happens in a microsecond.
The intensity of the shockwave is determined by the energy put into the device, usually measured in kilovolts (kV). A higher kV input means higher peak pressure and faster rise time. These two are the main determinants of the overall power and therapeutic effect of the shockwave.
Once generated the wave is directed into the body’s tissues. The effectiveness of the treatment depends on where this energy is focused.
Focused shockwave devices are designed to focus the acoustic energy at a specific location in the tissue. This brings us to two important concepts: the focal point and the focal zone.
The focal point is the exact single point where all the converging shockwaves meet. This is where the pressure and energy is at its highest. The clinical implications of this are:
The focal zone is the 3D volume around the focal point where the energy is strong enough to be therapeutically effective. This is not a single point but an area of treatment. Understanding the focal zone is important for:
In shockwave therapy "power" is not measured in watts like an electrical appliance. It’s quantified using acoustic energy parameters from pressure-time profiles.
The key parameter is Energy Flux Density (EFD), which is the amount of energy per unit area. When clinicians talk about the treatment "dose" they are often referring to the total energy delivered, which is the EFD multiplied by the number of pulses.
Note that the relationship between the device’s input voltage and the biological effect is not linear. Doubling the voltage does not simply double the effect, as the energy scales non-linearly.
Focused shockwave devices operate within specific ranges to be safe and effective. While the pulses generate huge pressure, the heat generated in human tissue is minimal. During a typical therapeutic pulse the temperature increase is usually less than 0.1°C which is negligible and ensures the primary effect is mechanical not thermal.
There are several ways to generate focused shockwaves, each with its own design and characteristics.
This is the oldest shockwave technology. It uses a spark gap submerged in a saline solution. When the spark fires it creates a pressure bubble that propagates as a shockwave. An elliptical reflector captures and focuses this wave towards the target tissue.* Pros: Can produce high energy wave.
These use hundreds or thousands of tiny piezoelectric crystals (often lead zirconate titanate, or PZT) on a concave surface. A high-voltage pulse makes the crystals expand and contract rapidly, creating small pressure waves that converge at a precise focal point.
This technology has evolved since 1988 and uses electromagnetic principles to generate the shockwave. There are three types:
Electromagnetic devices, especially the parabolic type, are known for their reliability, long lifespan (often over 1 million pulses per handpiece) and low maintenance.
Disclaimer: This information is for educational purposes only and is not a substitute for professional medical advice. Shockwave therapy should always be applied by a qualified clinician according to the device manufacturer’s guidelines and labeling.