NEW YORK — Can a workplace epidemic be cured?

With the personal computing boom of the 1990s came thousands of "repetitive stress injuries" or "repetitive strain injuries." RSI became the hip medical acronym of the keyboard era, with subset carpal tunnel syndrome the diagnosis of the day.

"At its height of diagnosis, anybody showing up at a doctor's office with wrist pain or hand pain was being diagnosed with carpal tunnel," said Carol Harnett, vice president of insurer Hartford Financial Services Group Inc.'s group benefits division.

Since then, carpal tunnel cases have plummeted, declining 21 percent in 2006 alone, according to the Bureau of Labor Statistics. Among workers in professional and business services, the number of carpal tunnel syndrome cases fell by half between 2005 and 2006.

What changed?

First, it may not have been the white-collar epidemic it appeared to be.

A 2001 study by the Mayo Clinic found heavy computer users (up to seven hours a day) had the same rate of carpal tunnel as the general population. Harvard University headlined a 2005 press release "Computer use deleted as carpal tunnel syndrome cause."

"Clearly, if keyboarding activities were a significant risk for carpal tunnel, we should have seen, over the last 10 to 15 years, an explosion of cases," said Dr. Kurt Hegmann, director, the Rocky Mountain Center for Occupational & Environmental Health. "If keyboarding were a risk, it cannot be a strong factor."

Blue-collar workers, especially those doing assembly-line work such as sewing, cleaning and meat or poultry packing, have a far greater incidence of carpal tunnel than white-collar workers, according to Bureau of Labor Statistics data.

That doesn't mean white-collar workers don't get carpal tunnel and related disorders. But it may mean such disorders were overdiagnosed when they were most in the news, resulting in an artificially high number of cases by the late 1990s. Most doctors have dropped the term RSI, calling them "musculoskeletal disorders" while government agencies like "cumulative trauma disorders."

Now, some experts think some of those patients had "referred pain" from trouble elsewhere, such as the neck. Other theories claim attention to ergonomics has prevented injuries or that they have become underreported because they lack the immediacy of a broken bone.

At the height of RSI-fever, it was hard to avoid. The National Institute for Occupational Safety and Health received three times as many requests for health and hazard evaluations related to wrist pain in 1992 than it did in 1982. During 1998, an estimated three of every 10,000 workers lost time from work because of carpal tunnel syndrome, according to the National Institutes of Health.

Some businesses have been focusing on prevention, part of a growing effort by employers to keep their workers healthy.

Outdoor clothing company L.L. Bean, Inc. shuts down its manufacturing line three times a day for mandatory five-minute stretches. Retailer Replacements Ltd. also runs on-the-clock group stretches as well as a fitness-walking program.

Blue Cross Blue Shield of Kansas started a program in 1991, when costs of the injuries to its employees passed $500,000. It bought ergonomic chairs and desks, introduced ergonomic assessments for new employees during their first two weeks of work and hired two full-time nurses to work with employees.

Since the program started, the company's workers' compensation costs have fallen by 62 percent, said Terri Janda, a nurse who leads the Blue Cross program.

As companies worked on interventions, ergonomics became cool. Auto companies advertised their cars' ergonomic features. Salons installed ergonomic hair washing stations. Everyone with a desk got a keyboard tray.

The Federal Occupational Safety and Health Administration introduced ergonomic standards in 2000, which were assailed by businesses claiming the standards would cost them somewhere between $20 billion and $100 billion to implement. The standard was overturned by Congress in 2001.