Aromatase inhibitors (hormone therapy) are used commonly in estrogen or progesterone-depending breast cancer to help prevent recurrence. They are very effective medicines and often help us avoid chemotherapy. Unfortunately they do have some significant side effects, including hot flashes, vaginal dryness, osteoporosis and joint pains. About half of patients develop some joint pain and stiffness, and about 10-15% of the time become severe enough that patients cannot continue treatment. This is a trial looking at a medication called duloxetine, or Cymbalta, that is used often for depression, anxiety or neuropathy. Patients with severe joint pains on hormone therapy were randomized to either duloxetine or placebo. More than half the patients treated with duloxetine achieved a clinically meaningful improvement in pain and improvement in joint stiffness. This may be an effective treatment to help patients with debilitating arthralgias stay on hormonal therapy.