Osteoporosis literally means porous bone. It is characterized by loss of bone density and the deterioration of bone tissue, which makes bones fragile and more likely to fracture.

The important thing about osteoporosis is figuring out whether you've got it before you injure yourself. And that's pretty easy to do: there's a specialized test that measures bone density, and based on its results, doctors can prescribe various medications to slow the disease down.

While osteoporosis is treatable, it's not curable, so early detection really is key. As it is, though, about one in two women, and one in four men over fifty will probably have an osteoporosis-related fracture. For women, in fact, the odds of suffering a hip fracture are the same as the combined odds of suffering breast, ovarian, or uterine cancer.

And hip fractures, especially, are very difficult to recover from--they're linked with a major deterioration in the person's health, to the point that about a quarter of folks over fifty who fracture their hips don't survive one year.

Treating all those fractures adds up. In 2001, direct medical expenses related to osteoporosis, like hospitalization and nursing homes, amounted to seventeen billion dollars.