Aetiology Of Tendonitis

* Overuse
Overuse injuries to tendons essentially demand too much from a tendon without allowing the tendon time to repair itself. Tendons, like most other tissues in the body, are nourished by blood flow. Certain areas of tendons have a poor blood supply, and, not surprisingly, these areas of the tendon are most prone to injury. That's why the Achilles tendon and the rotator cuff tendons are prone to injury. These tendons have an area of poor blood supply.

When tendons are used excessively, the body needs to be able to repair these tendons. Because of the poor blood supply in some tendons, this may take too much time. When the tendons are used excessively, the amount of damage make overtake the body's ability to repair itself. That's when overuse tendonitis develops.

* Trauma
Tendons can also become inflamed after a traumatic injury. In this situation, a single event may cause an inflammatory reaction within a tendon. If the inflammation is significant, the tendon may remain inflamed, and the acute injury can turn into a chronic tendonitis.

As with overuse tendonitis, if a traumatic injury is not allowed time to repair the damage and inflammation, a chronic condition can result. That is why rest is an important part of the treatment of tendonitis.

Occasionally, age can also play a role in tendonitis.
Another common cause of symptoms of tendonitis is due to age-related changes of the tendon. As people age, the tendons loose their elasticity and ability to glide as smoothly as they used to. With increasing age, individuals are more prone to developing symptoms of tendonitis. The cause of these age-related changes is not entirely understood, but may be due to changes in the blood vessels that supply nutrition to the tendons.

Calcific deposition could also contribute to the aetiology.

This condition is due to abnormal healing of the tendons. Normally, the tendon heals via the action of collagen forming cells known as fibroblasts. After a period of weeks or months, the fibroblasts become less numerous in the region and are replaced by osteoblasts (bone forming cells). These osteoblasts stimulate the growth of bone (calcium) in the tendon.

Hence the main reason for the development of calcific tendonitis appears to be delayed healing.

How does calcific tendonitis progress?
Calcific tendonitis usually progresses predictably, and almost always resolves eventually without surgery. The typical course is:

* Precalcification Stage
Patients usually do not have any symptoms in this stage. At this point in time, the site where the calcifications tend to develop undergo cellular changes that predispose the tissues to developing calcium deposits.

* Calcific Stage
During this stage, the calcium is excreted from cells and then coalesces into calcium deposits. When seen, the calcium looks chalky, it is not a solid piece of bone. Once the calcification has formed, a so-called resting phase begins, this is not a painful period and may last a varied length of time. After the resting phase, a resorptive phase begins--this is the most painful phase of calcific tendonitis. During this resorptive phase, the calcium deposit looks something like toothpaste.

* Postcalcific Stage
This is usually a painless stage as the calcium deposit disappears and is replaced by more normal appearing rotator cuff tendon.


One of the most compeling arguments is delayed healing. Normally, the tendon heals via the action of collagen forming cells known as fibroblasts. After a period of weeks or months, the fibroblasts become less numerous in the region and are replaced by osteoblasts (bone forming cells). These osteoblasts stimulate the growth of bone (calcium) in the tendon.

Hence the main reason for the development of calcific tendonitis appears to be delayed healing.