The decline in initiating treatment with any of the many medications known to reduce fracture risk is widely attributed to the outsize publicity given to the very rare risk of jaw necrosis and an uncommon fracture of the femur among patients who take bone drugs for many years. Yet the risk of a second hip fracture is far greater than either of these side effects, Dr. Bauer said. (The Food and Drug Administration just approved a new and different drug, Evenity, which builds bone, but it may have its own risks, this time a small increase in the chances of having a heart attack or stroke. Also, it is very expensive and may not be covered by insurance, and licensed only for postmenopausal women with a high risk of fracture.)

[Read more about a new osteoporosis drug that builds bone.]

In Dr. Desai’s study, treatment rates among those who broke a hip were even lower for men than for women, although men are nearly as likely to break another bone, including the other hip. In general, without preventive treatment, 15 percent to 25 percent of patients who suffer an osteoporotic fracture will experience another one within 10 years.

And with people living longer, hip fractures are increasingly likely. A report, published last year in the journal Osteoporosis International, revealed that, after a decade of declining rates of hip fractures, since 2012 the rates have plateaued in the United States, most likely because so many older adults, and their doctors, have turned their backs on bone-protecting medication. Among people enrolled in Medicare alone, Dr. Desai and co-authors wrote, this plateau “may have resulted in more than 11,000 additional estimated hip fractures between 2012 and 2015.”

The side effects associated with bone drugs “have gotten more hype than they should have,” Dr. Desai said in an interview. “People worry about them and with preventive therapy, they don’t see the benefits right away.”

However, Dr. Bauer wrote, “hip fractures represent only the tip of the iceberg; timely evaluation and consideration of drug treatment are appropriate for many other individuals at high risk of fracture.”

Many people at risk of breaking a bone because of osteoporosis are reluctant even to take vitamin D and calcium, nutrients critical to forming healthy bones. In a new national study reported recently by Dr. Spencer Summers, orthopedic surgeon at the University of Miami, to the American Academy of Orthopaedic Surgeons, fewer than one person in five known to have osteoporosis met the daily recommended intake of both vitamin D and calcium.

More than 10 million Americans have osteoporosis, and another 44 million are at increased risk of developing it. Osteoporosis, which means porous bones, is a chronic, progressive disease of increasingly fragile bones that can break from a relatively minor insult, like falling from a standing height.