This is an abnormal outward curvature of the thoracic vertebrae of the upper back. Compression of the front portion of the involved vertebrae due to osteoporosis leads to forward bending of the spine (kyphosis) and creates a hump at the upper back.
The cause is usually loss of bone mass or osteoporosis: women, in particular, develop this after menopause. This painful postural change is not just a sign of age, but it is an indication of advanced osteoporosis, which is when the vertebral bodies in the spine collapse and lose bone density due to loss of bone mass. These are called compression fractures.
Fractures of other bones without any recognizable cause or fractures that occur during everyday activities are an indication of possible osteoporotic disease. Hip fractures after minor falls and wrist fractures while supporting weight are most common. Ribs may even break while coughing.