Osteoporosis and MRI Study in Hemophilia

Inclusion Criteria: * Male and at least 25 years old at the time of screening * Moderately severe or severe hemophilia A or B (factor VIII or factor IX \<= 2% by chart documentation) * Ambulatory (ie, not wheel chair dependent) * Performance status - ECOG of 0 or 1 (= out of bed at least 75% of time) * Willing and able to comply with the requirements of the protocol and is able to give informed consent Additional inclusion criteria for MRI Substudy: * Baseline knee joint space width is \>= 3mm at the medial or lateral aspect of either knee as measured by weightbearing fixed flexion PA X-ray * Able to undergo 1.5 or 3T MRI Exclusion Criteria: * Inability to position properly for DXA * Presence of orthopedic hardware or other artifact in the lumbar spine (L1-L4) or either proximal femur * Prior documentation of being HIV positive * Radiosynovectomy or surgical synovectomy within the last 6 months * Current or past treatment with bone active drugs * Long-term corticosteroid use \[defined as 7.5-mg prednisone daily (or equivalent) for \>= 3 months\] * If subject is family member or employee of the investigator Additional exclusion criteria for MRI Substudy: * Any contraindication or relative contraindication to MRI * Less than 3mm knee joint space width at the medial and lateral aspect of both knees on baseline X-ray evaluation * Knee bleed within 30 days of informed consent * Prior total knee arthroplasty (TKA)