I started on Letrozole with no issues for 9 months until I began chemo and radiation duing which time I didn't take the medication. After, a different oncologist switched me to Anastrozole. It took awhile, but I began having severe joint pain centered mostly in my knees. I also became aware of the other issues so common as well. After a year, a new oncologist switched me back to Letrozole and I also started collagen supplements which took care of the knee problems which by then almost had me crippled. I've two more years on AI'S and will wait it out while on the Letrozole.