Blocking hormones (what aromatase inhibitors do) can cause the same troubling effects seen with low estrogen levels in surgical meno--now isn't that interesting? (free signup required to read)

Although this relates to contraceptives, it is pertinent to the relationship between hormones/hrts and autoimmune disorders in menopause as well. (free signup required)

While this article is about treatment of cancer with hormone-suppressing drugs, the effects of those drugs are similar to menopause with low hormone levels. It's interesting that symptoms doctors deny are menopausal are well known in relation to hormone-lowering treatment.

Of 612 women who responded, nearly all (96%) reported 1 or more adverse effects. About 30% of women reported discontinuing therapy, most of them (87%) because of intolerable adverse events and 47% because of joint-related problems. More than half of the respondents reported stroke, cough, swelling of arms and legs, flulike symptoms, and anxiety. Other effects included vaginal atrophy and dryness, a rise in cholesterol levels, and general pain. The full report and comments from respondents are available online. (free signup required)

Note that this doesn't really speak to system levels but rather levels of certain estrogen metabolites in urine, so that it is not at all more than a relationship, not a statement that estrogen/hrt cause or treat either the development or symptoms of knee osteoarthritis.