I was feeling similarly after a year on Anastrozole. My knees had me almost crippled. I switched to Letrozole and at the same time began taking collagen supplements. It was hard to tell which was responsible for my knees returning to normal until I accidentally bought a biotin supplement which did not include collagen. My knees began to ache, I realized my mistake and got back on the collagen and am almost to the end of my five years of AIs. I have some knee issues, but they are definitely arthritis related. I use collagen capsules for convenience but I've successfully used gummies and powder. I'm 69.