http://www.medicinenet.com/cortisone_injection/page3.htm
If I'm not mistaken it can make things worse in the long run.
Corticosteroids are CATABOLIC. This means that over time at high doses they essentially do the exact opposite of anabolic steroids. This really holds true for systemic corticosteroids, like oral prednisone.
That said, they do have their place in the body during times of stress and injury. Corticosteroids help control/decrease inflammation, help regulate blood glucose levels, and have effects on the immune system among other actions.
If there are problems with a joint--ie synovitis or inflammation of the synovia or a tendon sheath, corticosteroid injections can be a godsend becuase they will decrease inflammation and allow a return to normal activity. Just as an example, I screwed up my left shoulder when I was a freshman in college. After 5 months of dinking around with it, I could not lift my left arm to perpendicular to my body. I ended up going in for a full evaluation, where I was diagnosed with a partial rotator cuff tear among other problems. I was given two choices, surgery, or triamcinalone (corticosteroid) injections. I opted for the shots. I got back over 90% range of motion (I could put my left arm over my head) and was able to rehab things over the next several months. That localized antiniflammatory activity from the injection was exactly what I needed.
Basically I see them as a very good drug, if used under the right conditions at the right time.
