The majority of bone loss in individuals with spinal cord injury (SCI) occurs in the lower extremity (LE). The knee may reflect the state of bone health of the LE. Bone loss at the knee for various SCI groups compared to able-bodied controls is as follows: incomplete chronic SCI patients and men with acute complete SCI, 10% to 25%; men with chronic complete SCI, 33%; women with chronic complete SCI, 43%; individuals with SCI and pathologic knee fractures, 50%. Treatment modalities to increase bone mineral density (BMD) may be best evaluated by studying their effects on BMD at the knee in individuals with chronic complete SCI.