Low back pain is a common health issue in elderly population. According to the statistics, more than 80% of Taiwanese suffer low back pain in the life. The cause of low back pain includes lumbar spondylosis, osteoporosis, compression fracture, muscle strain, spondylolisthesis…etc. In addition to drugs and surgery, physical therapy is an alternative choice for conservative treatment. Therefore, in this study, the investigators propose to analyze the physical examination, diagnostic methods, X ray, physical therapy records, physical therapy methods and clinical outcomes in patients with the diagnosis including lumbar spondylosis, low back pain, osteoporosis, compression fracture, back pain treated at National Taiwan University Hospital and received rehabilitation at the Physical Therapy Center in recent ten years.