Was very worried about Prolia injections prescribed to counteract bone thinning of Letrozole from what I read online of side effects.Talked to several friends who have the injections none of whom had any issues .Also spoke to my GP who said he thought Prolia would be fine as he had many patients on it who also had no issues but he did say there could be joint pain issues from Letrozole. I also take 2 Caltrate Bone Health daily and been prior to breast cancer diagnosis.I also was told by Medical Oncologist I would need Calciumand Vit D tablets whilst on Prolia.I do get some joint issues but manage it ok with the above , a daily one hour walk which seems to enable me to walk thru the joint pain as it goes after a while walking , Plus I do a twice weekly gentle stretch and balance class. My guess is you may be taking an aromatase inhibitor like me and that is causing the joint pain but am not a doctor so would urge you to get it checked out.