8. To categorize the rheumatic adverse effects experienced by patients on aromatase inhibitors by specifically characterizing anatomic structures involved and documenting the presence or absence of inflammation in these tissues; to identify any correlations between changes in musculoskeletal symptoms and the duration of therapy with aromatase inhibitors; and to identify any correlations between changes in musculoskeletal symptoms and levels of circulating estrogen and its metabolites. This will be done at baseline and after one, three, six, twelve and 24 months of treatment.