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

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)

Osteoporosis and MRI Study in Hemophilia