Transient osteoporosis of the hip is a rare condition that causes temporary bone loss in the upper portion of the thighbone (femur). People with transient osteoporosis of the hip will experience a sudden onset (start) of pain that worsens with walking or other weight-bearing activities. In many cases, the pain increases over time and may become disabling. Painful symptoms gradually decrease and usually go away within 6 to 12 months. Bone strength in the hip also returns to normal in most people. Despite the name, transient osteoporosis of the hip is very different from the more common age-related osteoporosis. Age-related osteoporosis is a painless, progressive (develops over time) condition that leads to a weakening of the bones throughout the body. It can put people at greater long-term risk for broken bones.