Tendinitis is the inflammation of a tendon. When a tissue is damaged, it releases a chemical enzyme that breaks down the damaged tissues so that they can be re-built. If you sustain damage faster than the repair process can occur, you may get a lot of these enzymes being released. These may then irritate the healthy tissues, causing them to release enzymes, which attack more tissue. This is inflammation. When this occurs in a tendon, we have tendinitis. You can get tendinitis wherever you have a tendon that is being stressed.