I received cortisone injections for both shoulders because of tendonitis, arthritis and rotator cuff tear. Injections were given in the usual way- from the rear of my shoulders in the joint area as I am told. The pain had been inhibiting my lap swimming. It took about five days for the drug to take maximum effect. I then had about one week of almost total relief. However after this the pain returned more severe than before. During the period of relief I practiced a conservative regimen. Is it possible that an adverse reaction to the cortisone was responsible for the eventual return of the even more severe pain?