dowager's hump

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun An abnormal curvature of the spine that is primarily manifested as a rounded hump in the upper back and that typically affects older women. The curvature is the result of collapse of the spinal column caused by osteoporosis.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun The hump-like projection seen on the back of older people caused by kyphosis of the spine, consequent to osteoporosis; especially seen in women.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun abnormal spinal curvature that results when osteoporosis causes the spine to collapse; seen most often in elderly women