Bursitis is typically a reaction triggered by some sort of underlying injury or condition. This could be anything from a partial muscle tear to arthritis to an old injury that never quite healed in the past. This underlying injury may get re-aggravated or flared up, and cause your body to overcompensate, and produce too much synovial fluid. This synovial fluid goes into one of the many bursae you have all over your body and causes the pain and swelling associated with bursitis.
The best way to tell what kind of injury may be triggering your bursitis is to have a MRI, which should show any sort of soft tissue damage. You can use the ColdCure and the BFST to treat both your bursitis, and the condition that is aggravating your bursa.
More information:
http://kingbrand.com/Bursitis.php?REF=2160PV429.1522