1. To determine the prevalences of osteoporotic fracture in elderly Chinese population.
2. To determine the prevalences of osteoporosis in elderly Chinese population using QCT BMD measurement.
3. To investigate the difference in the prevalences of osteoporosis between cities and urban-rural area in China.
4. To investigate the association of body composition with osteoporosis
5. To investigate the prevalence of liver steatosis in China
6. To investigate the application of QCT fat measurement

Osteoporosis and osteoarthritis (OA) both are very common in elderly population,it is particular important for China with a huge aging population in the coming years.Bone mineral density measured by quantitative computed tomography (QCT) or dual energy X-ray absorptiometry (DXA) is the surrogate for bone health status and diagnosis of osteoporosis and OA. In this study we utilize the large-scale population based epidemiology study (PURE) population,spine and hip QCT and/or DXA will be obtained for the subject to investigate the prevalence of osteoporosis and osteoarthritis in elderly Chinese population. We also study the relation between bone mineral density with osteoporotic fracture and OA More than 3000 subjects selected from the PURE study participants in Beijing and other centers in China will be recruited to this study. More precisely, the subjects are consisted of the females over 55 years and males over 60 years old, along with the 20% randomly selected PURE participants for blood sampling.

Beijing ji shui tan hospital will be the coordinate center for the whole study, Beijing shi jing shan hospital, Beijing shun yi traditional medicine hospital and Taiyuan central hospital of shanxi will participate, other centers may be added late.

Bone mineral density of spine and hip will be measured with QCT and/or DXA. Quantitative computed tomography QCT pro (Mindways software, inc. USA) will be used for all QCT measurement, the CT scanner will be the clinical CT scanner of the local participated center.

Quality control and monitoring will be conducted by Beijing ji shui tan hospital, as well as the centralised image interpretation.

Therefore, this study is designed to provide the current and reliable prevalence of osteoporotic fracture, osteoporosis, OA in elderly Chinese population using QCT and/or DXA. The performance of QCT and DXA in the diagnosis of osteoporosis , as well as the association of body composition with osteoporosis will be assessed.

1. Inclusion Criteria:

   1. Participants of the PURE study in China (PURE China study)
   2. be willing to and be able to join in the study and signed Informed consent

2. Exclusion Criteria:

   1. Pregnant
   2. Spine and both hip implants

This is a population-based study, the population of this study is the subset of participants of the large-scale population-based study:the prospective urban rural epidemiology (PURE) in China.