Tendinitis

Tendinitis is a condition in which you overuse your joints and make them malfunction. Many piano players get this disease, but it is self made. It is not really a parasite, but more like overusing something. 
Cure
If you do not like this, then follow these steps:
* Wave arm
* Do a steeple stretch like moving, bend it. 
* Pull and push way
* watch how to master piano with Will Barrow.