Osteoporosis of spine. Coloured X-ray showing compression of one of the spine bones due to osteoporosis. Four vertebrae (spine bones) can be seen here in blue, with the top vertebra showing faintly. The second vertebra (second lumbar vertebra, L2) from the top has been compressed into an abnormal wedge shape due to weakening of the bone by osteoporosis. Osteoporosis is the loss of protein tissue inside bone, causing it to become brittle and easily fractured. The condition is a natural part of aging and leads on average to a one-third loss of bone density by age 70. When the spine is affected the vertebrae can crumble, causing pain, curvature and loss of height.