Letrozole Side effects and Knee Osteoarthritis

I took Tamoxifen for 5yrs without any side effects. I was then given Letrozole. After 6mths I noticed that the Osteoarthritis in my knees was worse. I mentioned this to the oncologist and he said it may have got worse even without the Letrozole. We agreed that I would carry on taking it and see him again after 6mths.It was a lot worse then so he agreed I should stop taking it. I have not been taking it for 5wks now but I have not seen any improvement yet. He did say it could take 2mths. Has anyone else had these problems with taking Letrozole?

I have been taking letrozole for over 5 years and feel much older than my 57 years. I have pain and stiffness in my knees, wrists and ankles and have pins and needles in my right hand. I didn’t have these problems before so I assume they must be related to the letrozole.

I’m not a medical person so only have a layman’s knowledge about this but I understand that the aromatase inhibitors like letrozole, arimidex and aromasin completely prevent the production of oestrogen in the body and can cause menopausal arthralgia - ie pain and stiffness in the joints. I understand studies are taking place to try and discover what the lack of oestrogen does to the joints and whether these effects are reversable or permanent.

I think these side effects may be more pronounced in people with existing arthritic conditions or those with a genetic tendency to arthritic conditions. ( My father suffered badly with osteoarthritis in his later years.)

I know some of the ladies on this site have found various preparations helpful in easing the pain. Sorry can’t remember what has been recommended but there is a recent thread on this section you might find useful.

I have secondary breast cancer so coming of letrozole has not been an option for me but it must be a very difficult decision to make if you have a primary cancer.

Take care

Wendy x


Thanks for your reply. Sorry to hear about your secondary breast cancer. I was interested to read that they are doing some studies to see whether the effects of a lack of oestrogen are reversible or permanent. My oncologist was quite definite when I spoke to him after taking Letrozole for 6mths that once you stopped taking it any side effects would disappear. I am not sure that’s the case now. I cannot believe that the osteoarthritis would have got this bad in such a short time. Unless my knees/legs show some improvement in the next few weeks I will probably never know whether the Letrozole was the cause.


Yes, my BCN told me that joint pains go away when you stop taking letrozole. But I understand that the body starts producing oestrogen again, which would be disastrous for those such as myself who have secondary bc. Fortunately the joint aches are manageable for me (I’m 58).


I was really hopeful that my osteoarthritis would be back to what it was before I started taking the Letrozole. It is 6wks now and I am doubtful that it is going to get that much better . How long ago did you both have your diagnosis of breast cancer the first time?
Hearing that both of you have secondary bc makes me wonder if I should have stayed on the Letrozole and put up[ with feeling 84 instead of 64. I have an appoitment to go back and see him in 6wks time.


Hi Marida,

What a difficult decision for you. My oncologist doesn’t know what to do with me now either as I have been on letrozole for over 5 years and they don’t really know as yet how long to prescribe letrozole for, especially for secondary breast cancer patients. At the moment, my oncologist is taking the easy option and doing nothing as letrozole has been so effective for me but who knows for how long or what damage prolonged use is doing to my body- although I suppose alive, stiff and creaky with thinning bones and hair is better than dead.

I was originally diagnosed in the " good old days " of 1990 ( I don’t think ) and treated with a lumpectomy and a good overdose of radiotherapy. Even though I was 39 and still menstruating, my lymph nodes were not tested, no attempt was made to stop my periods and I was not given tamoxifen. I had no follow up mammograms only manual examinations until just before I was discharged 10 years later in 2000. Amazingly I didn’t have a recurrence until 2002 when ER++, HER+++ secondaries were discovered. Who knows if this recurrence would have occurred if I had been prescribed Tamoxifen or aromatose inhibitors from the start. I remain reasonably well, my current health problems seem to be caused by the after effects of previous radiotherapy and current medication.

I think it is so much harder for people diagnosed in the past few years with the proliferation of treatment choices and accessible ( though often incomprehensible ) knowledge from the internet.

Please let us know what your oncologist recommends at your next appointment.

Take care.

Wendy x

Hi I am six weeks in from starting Letrozole and am suffering pain in my knees although I had an occasional problem with one or other now I am having trouble standing up after sitting down, I walk our dog nearly every day so do get moderate exercise. I see my oncologist on the 22nd of feb be interested to see what he says then.

I had 21/2 years of joint pain and stiffness with Letrozole. I felt old before my time but didn’t contemplate stopping it. This summer I had a second tumour so letrozole wasn’t working or had stopped working for me. After treatment I was put on exemestane. My aches and pains are much less on this drug and I don’t feel as fatigued and depressed by chronic pain. It just goes to show that they are all inhibitors but different ones suit different people. Perhaps if one doesn’t suit you could ask to try another? 

Dont know if this pain is osteoporosis starting… taking Letrozol for 6 months and I’m feeling so disabled, using a walking stick to get around the house, I had problems previously following a brain haemorrhage 31 years ago used a wheelchair outside but never suffered pain like this.  I’ve tried Ibroprufen, paracetamol, drinking cherry juice and just rubbed deep heat into my knees and lower leg.   Any more sugggestions I’m on this for 10 years.  Oh have had lumpectomy one lymph node removed and Radio therapy.   Heeeeeelp please.

Yes! In fact I am awaiting knee replacement as well, because there is no cartilage left in either knee. However lately the pain has intensified. I was just thinking it was from both knees being so bad now I’m beginning to wonder. I think I’m going to talk to my oncologist and tell him I need to take a break from it as well period however because I have had 3 tumors metastasize to my brain in the past year they may not want me to stop just yet. But I tell you I cannot continue with this pain I have to do something. I can’t even sleep at night because the pain is so severe.

I have been on Letroole for 3 months and had to have 30cc of blood drawn off my knee yesterday.

It seems my quality of life steady goes down with each pill