The doorknob’s days are numbered. You know this. You find your hand clenching a doorknob and twisting it less often. More often, you just push down on a lever, whether it’s a simple 5-inch bar or a brass handle curved with the elan of a dog’s tail. The compelling argument for door levers is a practical one: When you’re struggling with too many bags or with arthritis, the lever’s easy-release mechanism sparks a little gratitude. Heck, an elbow works when your hands are full. Knobs, on the other hand, provoke no emotion other than frustration.

Because few people, decorators aside, get up in the morning feeling that they simply must do something about their doorknobs, it’s a slow revolution. But levers now account for 15 percent of U.S. door-opener sales for homes, according to hardware industry surveys, and double that in the market’s high end.

A powerful federal law is fueling the revolution, along with the aging of the U.S. population. Also key: a gap between lever and knob prices that’s shrinking as levers become more popular.

"For us, in the high end or medium, it’s always levers now," said Mary-Lynn Hall, a project designer at Phoenix’s EXPO Design Center, the upscale offshoot of Home Depot.

That’s not true for Home Depot, where most customers are looking for replacement knobs. But levers are surging in the new-home market, according to Aaron Davis, a dealer division manager at Builders’ Hardware and Supply, Seattle’s biggest door-hardware wholesaler.

Before 1990, Kwikset, Schlage and other big U.S. door-hardware manufacturers turned out almost no levers. Then came the Americans with Disabilities Act.

Under guidelines for complying with the act, the doors to public buildings must be "usable with one hand, without tight grasping, pinching or twisting of the wrist." That killed the doorknob market for U.S. hotels, restaurants, stores, hospitals and nursing homes, as well as condominiums, airports, commercial and government buildings and schools.

Levers – long standard in Europe – proved to be the most popular alternative.

"Initially, they were a lot of trash because U.S. manufacturers were unprepared for the transition," said David Lowell, the director of training and certification for Associated Locksmiths of America, based in Dallas.

Differences between commercial and residential door-hardware requirements slowed levers’ transition to private homes. That’s mainly because commercial doors, which are likely to be used hundreds of times daily, require heavier-duty and costlier hardware than residential doors do.

The price gap between levers and doorknobs is now down to 20 percent or less, according to Davis. It’s still big enough to keep levers out of low-priced homes, whose builders shave all costs. But innovations in home products typically start at the high end, then broaden their appeal and drop in price before becoming mass-market items, said Minu Youngkin, a residential advertising and communications manager at Schlage.

"In hardware, this used to take 15 to 20 years," she said. "Now it’s more like 10 years from high end to mass market."