Abnormal femur morphology Low femoral bone density 2017-06-18T17:59:29Z Osteopenia is defined as BMD between 1 standard deviation (SD) and 2.5 SD below the mean of the young reference group. Osteoporosis is defined as BMD 2.5 SD or more below the mean of the young reference group. Reduced bone mineral density of the femur. Low femur bone density