I am new to this site but have read some of the posts and wanted to see if someone could offer some more info on my situation. A recent MRI of my shoulder found bone erosion in my ac joint. This was after about a year of pain and 2 neg. plain x-rays. I am 44 yo female with no prior injury to the shoulder. A year ago, RA test neg, and only found to have low vitamin D level for which I now take 50000 units weekly. Is Erosion only found with RA or could it be OA? I am so confused. Any advice?