Approximately 85% of individuals with Mucopolysaccharidosis (MPS) type I, II, or VI report weekly pain and 50-60% have significant limitations in their activities of daily living due to MPS related musculoskeletal disease despite treatment with enzyme replacement therapy (ERT). Thus there is a critical need to identify additional therapies to alleviate the burden of musculoskeletal disease in order to improve the health and quality of life of individuals with MPS. However, disease progression needs to be quantified to be able to determine efficacy of new therapies. This study is a multi-institutional, 5-year, longitudinal study of musculoskeletal disease in MPS. The objective is to quantitatively describe the progression of skeletal disease and identify biomarkers that either predict disease severity or could be used as therapeutic targets in individuals with MPS I, II, and VI. A database of standardized measurements of musculoskeletal disease in MPS will allow the field to efficiently move forward with therapeutic clinical trials in patients with MPS.