I have been taking Arimidex for about 7 weeks with some side effects, but I know it could be worse. However, today I have developed extreme pain in the crease of my thigh. I understand AIs may causes joint pain, but it seems like such an odd joint to hurt. I mean out of all the joints . . . the crease of my thigh? Also, what cause the joint pain -- do AIs affect ligaments, tendons, etc.? If I have to describe the pain I am feeling, I would say it was in the crease and not in a bone. Just to reiterate . . . the pain was quite severe as I had trouble walking.