What Causes Joint Pains While On Methadone?

My daughter (47) is on Methadone - she has been prescribed this for the last 8 years "for pain". She is living with me and among other issues is very moody and gets highly irritable at times. My major question is this - yesterday morning she woke up and was in agony with pain she said in all of her joints knees, arms even her finger joints. Does this "crap" that dr's have prescribed to her have this kind of effect? A very sad and concerned Mom