Mine was in the first couple of weeks. For some it starts to subside by the second month. Mine didnt, but many have hardly any after a while.

I’ve had many MANY different symptoms. A few started right away. Some have subsided enough to deal with but others continue and are getting worse. I have taken each symptom as it has come and tried to take measures to get relief from each. Have you tried epsom salt baths. Try a long soak about an hour or so before bedtime. Make it relaxing and comfortable, soothing music, a towel behind your head, whatever works for you. Maybe some slow deep stretches of the muscles that bother you the most. Best of luck to you! We all have a hard road to travel so take care of yourself. We are here to vent and support one another.

What time of day do you take your AI? I started seeing symptoms about 6 weeks after taking Letrozole. Muscle aches in my arms and joint pain in my hands and lower back. I first tried taking it at night, but have switched to the AM and the night pains are much better. My worst side effect is the uro-gyno atrophy (drying and thinning of vaginal and urinary tract tissue). I had 3 major urinary tract infections in four months and very painful intercourse. Have tried the Bonafide vaginal inserts, but not very helpful. I have found that staying active (walking 2-3 miles in the neighborhood 3-4 times per week), stretching and yoga, and staying hydrated have helped tremendously with the stiffness and back pain. Still have some mild hot flashes, but not as bad as menopause (I'm 64 now). I have been on letrozole about 15 months and plan to continue if the side effects stay status quo.
Also for those with brain fog, have you had your thyroid, D3, and/or B12 levels checked? A year before my BC diagnosis, I was having terrible brain fog, digestion issues, and neuropathy in my right leg. Finally went to the doctor and found I was very low on both vitamin levels and was hypothyroid. Once I started taking D3 and B12, my brain fog lifted and I was back to my old self. I started on probiotics and changed my diet to gluten-free, dairy-free, and soy-free and my digestion issues and thyroid levels are better, plus I lost 45 lbs! Definitely worth checking into!

@wyngnit My aches started about a month on Anastrozole. I stayed on it for six months I could barely walk some days. When I told my doctor how I felt she told me I should have never gone that long. Thought I was toughing it out apparently I was wrong. She switched me to Tamoxifen tried it didn't like that either and now I don't take anything. Not saying I've made the correct decision but quality of life is important to me.

I took anastrozole for 7 weeks. From what I read about it, side effects can manifest within the first few days. I had immediate (by day 4) side effects that weren't onerous (mild hot flashes, a lot of deep muscle twitching that felt like pre-clamps but didn't develop into serious cramping, and a sudden onset of headaches). In week 3, I developed, pain on my hip that was bad enough that I couldn't stand on my right leg. I stopped taking the meds and the pain left on day 3 of discontinuance. I resumed the anastrozole a week later and the hip problem reappeared on day 4 of trying it the second time. I'd never had any pain in that hip or weakness in that leg to otherwise account for the pain. It might have eased up after a few months on the meds but my risk of recurrence is low if the genetic assays and stats are low so I discontinued them. But will do frequent blood work for key indicators and tumor markers to monitor any changes with those. If we see a bad pattern from that or any exam or test, I'd have to reconsider taking AIs. If I did take one, I'd likely have to start on drugs to try to prevent bone loss and that bothers me as those choices aren't without side effects either. It's a bit of a Hobson's choice either way for me.