Tendonitis refers to a sterile inflammation of the tendon itself or its surrounding sheath caused by various reasons. The term "tendonitis" means that, firstly, the affected area is either the tendon or the surrounding tissue. Secondly, it is a sterile inflammation. The causes of tendonitis are generally the following four points: The first point is acute injury. The second point is chronic overuse. The third point is an increased load on the tendon itself, causing some micro-damage inside the tendon. This leads to inflammation due to bleeding and inflammatory irritation in the tendon or around the tendon. The fourth point involves prolonged exercise or excessive exercise load, which then leads to congestive hematoma around the tendon, ultimately leading to inflammation.