A shockwave is essentially a pressure disturbance that propagates rapidly through a MEDIUM.
It can be defined thus: A large-amplitude compression wave, as that produced by an explosion or by supersonic motion of a body in a medium which just a formal version of the first sentence.
A clinically useful shockwave is effectively a controlled explosion, and when it enters the tissues, it will be reflected, refracted, transmitted and dissipated like any other energy form. The energy content of the wave will vary and the propagation of the wave will vary with tissue type. Just like an ultrasound wave, the shock wave consists of a high-pressure phase followed by a low pressure (or relaxation) phase. When a shock wave reaches a 'boundary', some of the energy will be reflected and some transmitted.
The following are the most strongly established treatment effects at therapy shockwave levels:
Increased local blood flow
Increase in cellular activity – the release of substance P, prostaglandin E2, NO, TGF β, VEGF, and almost certainly other inflammatory cytokines
Transient analgesic effect on afferent nerves
Break down calcific deposits (primarily, but not exclusively in the tendon)