The basic design of artificial joints has not changed for decades. But increased volume — about one million knee and hip replacements are performed in the United States annually — and competition have not lowered prices, as would typically happen with products like clothes or cars. “There are a bunch of implants that are reasonably similar,” said James C. Robinson, a health economist at the University of California, Berkeley. “That should be great for the consumer, but it isn’t.”

‘Sticky Pricing’

The American health care market is plagued by such “sticky pricing,” in which prices of products remain high or even increase over time instead of dropping. The list price of a total hip implant increased nearly 300 percent from 1998 to 2011, according to Orthopedic Network News, a newsletter about the industry. That is a result, economists say, of how American medicine generally sets charges: without government regulation or genuine marketplace competition.

“Manufacturers will tell you it’s R&D and liability that makes implants so expensive and that they have the only one like it,” said Dr. Rory Wright, an orthopedist at the Orthopedic Hospital of Wisconsin, a top specialty clinic. “They price this way because they can.”

Zimmer Holdings declined to comment on pricing. But Sheryl Conley, a longtime Zimmer manager who is now the chief executive of OrthoWorx, a local trade group in Warsaw, said that high prices reflected the increasing complexity of the joint implant business, including more advanced materials, new regulatory requirements and the logistics of providing a now huge array of devices. “When I started, there weren’t even left and right knee components,” she said. “It was one size fits all.”

Mr. Shopenn’s Zimmer hip has transformed his life, as did the replacement joint for Mr. Catugno, a TV director; Ms. Foley, a lawyer; and Ms. Nelson, a software development executive. Mr. Shopenn, an exuberant man who maintains a busy work schedule, recently hosted his son’s wedding and spent 26 days last winter teaching snowboarding to disabled people.

His joint implant and surgery in Belgium were priced according to a different logic. Like many other countries, Belgium oversees major medical purchases, approving dozens of different types of implants from a selection of manufacturers, and determining the allowed wholesale price for each of them, for example. That price, which is published, currently averages about $3,000, depending on the model, and can be marked up by about $180 per implant. (The Belgian hospital paid about $4,000 for Mr. Shopenn’s high-end Zimmer implant at a time when American hospitals were paying an average of over $8,000 for the same model.)

“The manufacturers do not have the right to sell an implant at a higher rate,” said Philip Boussauw, director of human resources and administration at St. Rembert’s, the hospital where Mr. Shopenn had his surgery. Nonetheless, he said, there was “a lot of competition” among American joint manufacturers to work with Belgian hospitals. “I’m sure they are making money,” he added.