Bone & Joint

The bones become lighter and more brittle because of a loss of calcium. This loss in bone mass is greater in women than men after the fifth decade. In joints the cartilage covering the ends of bone becomes thinner and sometimes disappears in spots, so bone meets bone directly and the old joints creak. Compression of the spinal column can lead to a loss of height.

Joint replacements, particularly at the hip, and bone fixation devices have become very successful applications of materials in medicine. The use of pins, plates, and screws for bone fixation to aid recovery of bone fractures has become routine, with the number of annual procedures approaching five million in the United States alone.

Calcium is not the only thing in milk that is good for bones, a study suggests. A protein present in cow's milk, as well as in human breast milk, stimulates bone-forming cells in laboratory dishes and induces bone growth when injected into mice, researchers have found. The molecule, an iron-binding protein called lactoferrin, could form the basis of a new treatment for osteoporosis, says study leader Jillian Cornish of the University of Auckland in New Zealand.