Yes, Tamoxifen comes with its own set of side effects that are not that great. I had a hysterectomy years ago so felt it might be ok to try the Tamoxifen. I still feel the night sweats but they aren't really bad. I am taking Tamoxifen at night but maybe I should switch to morning. The muscle aches are still present in my shoulder/neck but a lot less and more tolerable than when taking the AI drugs. So, this much is tolerable. But we both know that sometimes the effects get worse in time when taking these meds so we'll see. But I too think that if things get worse with joint pain/muscle issues I would consider stopping. I do hope you can find something to help with your knees. Best wishes.