Osteoporosis and osteopenia are characterized by reductions in bone mass, and may lead to skeletal fragility and fracture. Until the advent and widespread use of such methodology to measure bone density, such as dual energy X-ray absorption (DXA), the definition of osteoporosis was usually made using the clinical signs of a fracture. In 1994 the World Health Organization defined osteoporosis as a bone mineral density level more than 2.5 standard deviations below the mean of young normal women (WHO, 1994). The potential inter-relationship of the two diseases will be discussed in this paper.