Tennis elbow, also known as Lateral Epicondylitis, occurs at the outer edge of the bony point of the elbow. It is a common overuse injury which was originally named due to its frequent occurrence in tennis players. However, anyone who may use their arms and hands a lot can experience this - Musicians, plumbers, weight lifters etc...
Microscopic tears in the common extensor tendons of the hand, particularly at the attachment point on the elbow, along with poor recovery results in poor healing of the tendon.
As the injury continues into a chronic state, the tissue changes and becomes thickened and disorganised. This further prevents the area from healing. As the area is not necessarily inflamed, it won't respond to anti-inflammatory treatments.
Shockwave can reverse these changes, stimulate controled inflammation and, therefore, healing of the tendon.