Cortisone shots are funny things. ~15 years ago I injured my right shoulder while chainsawing and moving trees. After 3 months, it wasn't getting any better, so I saw a sports medicine doctor who diagnosed "schmutz" in the joint, and pushed this big honking needle in my shoulder. A week later, the pain was completely gone, and has never returned.
On the other hand, two years ago my left elbow was hurting as the result of shoveling too much snow, and I remembered how well the shoulder had done. A shot to my elbow hurt like hell when the anesthetic wore off, and there was only modest improvement for a few weeks before it was back where it was before the shot. Then I decided to search for the effectiveness of corticosteroids for tennis elbow, and was horrified to learn that they are less effective than placebo, and actually increase the risk for long term injury by weakening the tendon.
Surprisingly, after 3 months of heavy lifting involved with moving my household earlier this year, the elbow is back to normal. I also suspect that using a touchpad on a laptop contributed to the problem, and have cut back on that repetitive movement.