Some of the victims are easily recognized --

the stooped shouldered, humpbacked little old lady, shuffling slightly as she walks. Look closely and you will see that her arms and legs seem disproportionately long for her upper body. You are seeing right. The condition can rob as much as eight inches in height, all from the spine.

The condition is osteoporosis, an acceleration of the natural loss of bone mass that accompanies aging. Osteoporotic bones become so brittle and porous that a break can occur with the most minor trauma, like lifting something light, or sometimes for no apparent reason at all.

In some instances, osteoporosis results from clearly identifiable diseases, drugs or injuries. But only 15 percent of all sufferers are in this group. For the rest there is no known cause, although there are several prime suspects.

Estimates indicate 20 million people in the United States have it, many without knowing. It causes approximately 1.3 million fractures every year.

Women, who lose bone sooner and at twice the rate of men, are most at risk. Complications arising from broken bones, particularly hips, are the third leading cause of death among the elderly. One estimate places the annual cost of health care, social services and lost work hours at $3.8 billion.

"Wouldn't you think the name of a disease that affects half the women 45 years of age would become a household word?" writes Dr. David F. Fardon, author of one of three new books on osteoporisis.

All the books take the reader's eye off the skeleton and into the living bone, a perception new to most of us.

For children, growth is the business of bones. But bone production peaks in adolescence, triggered by a surge in sex hormones. Once a person reaches a fixed height in adulthood, bones no longer grow in length, but constantly recycle themselves by a process called remodeling. Dr. Morris Notelovitz, one of the authors of "Stand Tall!," writes that the cycle lasts three to four months, and each year adults have 10 to 30 percent of their bones replaced. When this continuous cycle is knocked out of balance, osteoporosis develops.

The three books present a similar portrait of who is liable to develop the condition. You are at risk if you are old, female, post-menopausal (naturally or due to a hysterectomy), petite, fair-skinned, childless and there is a family history of the condition. You cannot do much about these -- except maybe have a child.

Risk factors which are within your control include: nicotine, alcohol, caffeine, lack of exercise and poor nutrition.

Just as the first risk factors only indicate who might be at risk, however, taking control of the other areas is not an absolute guarantee against osteoporosis.

One thing is certain: it is critical to enter adulthood with maximum bone mass since some age-related bone loss is inevitable. Adolescent girls and pregnant women especially must eat well and pay special attention to calcium consumption.

Once bone mass is lost, it cannot be restored. So, although it's a disease of old age, osteoporosis must be fought when a woman is still young.

Unfortunately, advice does not come in a neat package. All three books describe the exquisite nature of the remodeling process but conclude that no one knows how to keep it in balance.

Good nutrition and regular exercise definitely help. Calcium requirements have been established, but each book suggests a different amount.

The recommended amount falls into a range of 800 to 1,500 milligrams daily. Fardon and Smith argue that postmenopausal women need 1,500 mg., while Notelovitz and Ware recommend 1,200-1,400 mg. Growing children need 1,200 mg daily.

Whatever the recommended amount, many women consume only 450 mg. of calcium daily and that is not enough.

A woman can't even protect herself by simply eating more foods that contain calcium. The body normally absorbs only 10 to 30 percent of the calcium it obtains from food.

The hero in all this is milk, preferably the skimmed, low-sodium variety. One cup of skim milk has either 300 mg of calcium (Smith) or 296 mg calcium (Notelovitz).

Any one of the books is worth reading if you don't know anything about osteoporosis.

Fardon's was the most informative, but it was also the most difficult to read. His training and experience as an orthopedist are reflected in the depth of information conveyed.

Wendy Smith, a lay medical writer, wrote a straightforward book with pamphlet appeal. But the short text of the book does not capture some of the nuances and complexity captured in the other two and tends toward oversimplification. She does provide a month's worth of calcium rich menus and recipes which some readers might find useful.

Notelovitz is director of the Center for Climacteric Studies which specializes in disorders which begin in mid-life. This background (along with Marsha Ware's who worked at the center) comes through in a book that is wonderfully people-oriented. Packed with charts, illustrations, clear explanations and exercises, it was the most engaging of the three. Since it is a reissue of a 1982 hardback, however, it lacks some up-to-the-minute information.

Any one of the books is must reading if you are a woman.