I’ve been taking Letrozole for seven years. I have no joint pain or aches at all but it has had an effect on my bone density. I am now nearly 75 so some of this may be natural but my bone density at 68 was extremely good (levels expected in a 35 year old according to my oncologist) so Letrozole has had an effect. You would certainly be wise to have a bone density test before you start, if you haven’t already done so. I am having an annual test tomorrow so we’ll see how we go. I have no osteoporosis but osteopoenic patches, which fluctuate a bit (were actually improved last test). Unfortunately research doesn’t say if 7 or 8 years is better than 5, just that 10 is better than 5. Bone density impact seems fairly common but joint pain does seem to vary enormously so you may not know about that till you have been on a it a while. Some also find Letrozole vacations (going off for a month or so) can help. Best wishes.