The patient is a 60 year old woman with a long history of low back pain. She has been treated with prednisone since 1974 for rheumatoid arthritis with thenar muscle wasting. She also has osteoarthritis of the large joints. She received an epidural injection into the lower spine for pain but the pain became worse.

1. What is your differential for lower back pain in this woman?

2. Why might pain the pain have become worse after injection?