Knee replacement with Severe Osteoporosis

I was a candidate for tkr 2 yrs ago and was on the schedule but I chickened out. I felt that the pain did not warrant the surgery. Recently I've had 2 horrendous flare-ups. I was not able to bear weight on my right leg and had to resort to a walker for about a day and a half. The 2nd flare-up happened a month later and that one had to use walker for about 4 days. Prior to these flare-ups I had no major flare-ups like these. I decided it's time. Here's the challenge: I have severe osteoporosis (spine -4.7, r femur -3.6 and l femur -2.9) I saw 2 Endocrinologists who want me to go on Evenity. The only other drug I can go on is Tymlos. They want me to go on a bone building drug. I am bone-on bone in both knees. I've been waking up with pain once or twice at night sometimes in one knee, sometimes in the other or both since I've had these flare-ups. I don't want to wait too long to get the tkr. I'm thinking I should be on Evenity for min of 6 mos before the surgery.

If there is anyone out that there has had a tkr while being on Evenity, please let me know your experience. Much appreciated.