WASHINGTON — Gangrene was eating away Frank D. Johnson’s toes, the last stage of a little-known disease that slowly chokes off blood flow in millions of people’s legs.Dr. Richard Neville made a last-ditch attempt to avoid amputating his leg, implanting a special woven tube to replace a key clogged artery. The artificial blood vessel, coated with a blood-thinning drug to work better, is the latest treatment aimed at saving legs riddled with peripheral artery disease, or PAD.

Far better would be to stop this disease before patients’ legs are in such jeopardy, not only to keep the people walking, but because having the leg condition increases sixfold the risk of a heart attack or stroke. If leg arteries are clogged, other blood vessels usually are, too.

Now a major push is on to get more people checked for PAD — with the message that trouble walking isn’t a normal part of aging — and to test just which early stage therapy is best at stemming the disease before it imperils a leg.

“PAD has been woefully underdiagnosed and underappreciated,” says Neville, vascular surgery chief at Georgetown University Hospital. “Pain in your legs is not something you have to live with, not just a part of getting old.”

PAD afflicts up to 12 million Americans as their leg arteries stiffen and narrow. Eventually, the lack of blood flow to muscles causes an aching pain while walking, called claudication.

Worse, if arteries become completely blocked — an emergency called critical limb ischemia — ulcers, infection and gangrene can set in. That leads to 75,000 to 150,000 amputations a year. And when PAD patients lose a leg, their risk of premature death skyrockets as they become even more sedentary, sometimes bedridden.

Anyone can get PAD. But diabetics are particularly vulnerable; one in three over age 50 is likely to have it. So are black Americans, who have twice the risk of whites.

Just getting older increases the risk; about one of five Americans over age 70 has PAD. Other risks include high blood pressure or cholesterol, having ever been a smoker, or having heart disease.

A simple check — feeling the pulse at the ankle and comparing blood pressure in the ankles and arms — is enough to signal the possibility of PAD.

That easy foot check is probably just as important as listening to the heartbeat, says Dr. Alan Hirsch, vascular medicine chief at the Minneapolis Heart Institute. Yet it’s not a part of most checkups even for people with obvious risk factors, something a new $2 million campaign by the National Institutes of Health and the PAD Coalition that Hirsch heads are working to change.

“We don’t seem to take our legs very seriously,” says Hirsch, who laments that between the 15-minute checkup and patient reluctance to complain, leg health — and thus a window into heart health — gets overlooked. “We hope the campaign will create a major paradigm shift.”

Among the efforts: NIH-created radio ads that aim to correct the myth that trouble walking is normal as you get older, and efforts to ensure that once the legs are treated, doctors monitor PAD patients’ heart health, too.

But how to treat PAD? This month, doctors around the country began recruiting 250 claudication patients for a first-of-its-kind study to determine the best strategy for earlier-stage disease: the drug Pletal; special exercise therapy; artery-widening angioplasty; or some combination.

Some newer technologies, like a tiny razor that shaves clogged arteries and a laser to blast away the sludge, promise help, too.

But thousands of PAD sufferers are like Johnson, with severe disease hastened by high blood pressure and kidney failure at a young age. Last May, the Birmingham, Alabama, man danced at his daughter’s high school graduation. But by August, he had so little blood flow in his left leg that doctors performed bypass surgery to replace the clogged artery with one of his own clog-free veins.

It failed, and at 49 Johnson was facing amputation.

Cancel that operation, ordered his sister, who happened to work at Georgetown — and drove Johnson up for a second opinion with Neville, who was excited to try the newly approved artificial blood vessel.

Called Propaten, it’s not the first manmade blood vessel, but previous ones re-clogged quickly, Neville says. Propaten is coated with the blood thinner heparin, and he cited data from Europe suggesting it may work better for certain hard-to-treat cases.

“My own bias is it’s not as good as a vein, but it’s the closest thing we’ve got,” says Neville. “I think it will allow us to save legs that might have been lost.”

Indeed, a few weeks after Johnson’s implant, he’s losing a few toes from the gangrene, but Neville expects him to walk again.

“He’s back to his fighting self,” said his sister, Lucile Harvey.