Do your thumbs hurt? If you're sending lots of text messages, you may have the trendiest new malady: "Blackberry thumb (search)."

Yes, you can peck out text messages with any finger. But users of popular wireless devices such as the Blackberry type much faster by pecking out messages with their thumbs. Many people soon learn to type 40 words a minute.

Whatever your thumb-typing speed, lots of messages mean lots of repetitive thumb motions. And that could mean trouble, says Alan Hedge, PhD, director of the human factors and ergonomics research group at Cornell University in Ithaca, N.Y.

"The thumb is not a very dexterous part of the hand," Hedge tells WebMD. "It is really designed as a stabilizer for pinch gripping with a finger. That is why you only have two of them, not eight. It is the fingers that have dexterity, not the thumb."

The full-size keyboard was designed with this in mind. One uses one's dexterous fingers for lightning strikes on the letter keys. One reserves one's relatively clumsy thumbs for the humble task of striking the spacebar.

"When you switch that around, you put a lot of strain on the thumb," Hedge says. "So if you persist in typing a lot of information with your thumbs, you risk injury."

Hand surgeon Prosper Benhaim, MD, associate professor of orthopaedic and plastic surgery at UCLA, agrees that too much thumbing could be injurious.

"Anything that causes repeat motion can predispose someone to injuries of various sorts, whether it is tendinitis or aggravating underlying arthritis," Benhaim tells WebMD. "These things can be made worse or even initiated by overuse. But thumb typing is very repetitive, and the keys are so small it makes it difficult to navigate around easily. Because it is so small, people are likely to press harder vs. a larger keyboard. So the thumb on the Blackberry does more than you would do with your fingers on a keyboard.'

Blackberry Thumb: Tendinitis, Aggravated Arthritis

What kinds of injuries are possible?

"Blackberry users include a significant segment of the population old enough to be developing arthritis (search) – and this can aggravate it," Benhaim says. "And there different types of tendinitis (search). One is trigger thumb. The other is de Quervain's tenosynovitis (search), involving the tendons on the side of the wrist right where the forearm joins the wrist. These tendons participate in controlling the thumb and are very sensitive to repetitive motions."

These kinds of injuries are not new. Back in the 1980s, these injuries had a different name – and a different blame, says hand-injury specialist Gary McGillivary, MD, assistant professor of orthopaedics at Atlanta's Emory University.

"This is like what they used to write about Nintendo thumb – they called it nintendonitis," McGillivary tells WebMD.

Video game players have sometimes come down with rather serious injuries, says David A. Allan, MD, PhD, director of the repetitive strain injury center and supervisor of occupational medicine at the University of Pennsylvania's PresbyterianMedical Center in Philadelphia.

"I saw one kid who just played and played video games for seven hours at a stretch," Allan tells WebMD. "His thumb was only a small portion of his problem – his whole arm was affected." Allen says the child had nerve damage in his shoulder as well.

But it's rare for repeat motion injuries to involve long-lasting nerve damage, Allan says.

Blackberry Thumb Rx: Rest Your Weary Digits

What's the treatment for Blackberry thumb? Lay off thumb typing, the experts tell WebMD.

"If they have true tendinitis, I might give them a cortisone shot," Benhaim says. "Or I might use a thumb brace, maybe. I would certainly tell them to rest it. And then to minimize the stress and strain. Do more typing on your keyboard and then sync over to your Blackberry rather than typing longer messages on Blackberry itself."

Merchandisers have been quick to cash in on the trend. Several thumb splints and glove-type treatments are available. But Allan warns that these quick cures may actually aggravate the problem.

"With the thumb splint, it is very iffy that it will change the mechanics of the motion to make it better. And it might make it worse," he says.

Blackberry Thumb Epidemic?

All the media fuss might lead you to think that there's an epidemic under way. Not so, Benhaim says.

"I do not think it is as big a deal as people say. I've seen video-game thumbs a lot, but no there's no epidemic," he says.

In fact, none of the hand experts who spoke with WebMD has seen a single patient with Blackberry thumb.

"I haven't seen it," says Benhaim.

"I haven't seen any patients with this," says McGillivary.

"Nobody has yet been referred to me with Blackberry thumb," says Allan.

By Daniel J. DeNoon, reviewed by Brunilda Nazario, MD

SOURCES: Gary McGillivary, MD, assistant professor in orthopaedics, Emory University, Atlanta. Alan Hedge, PhD, professor of ergonomics; director of Human Factors and Ergonomics Research Group, Cornell University, Ithaca, N.Y. Prosper Benhaim, MD, associate professor of plastic surgery and orthopedic surgery, University of California, Los Angeles. David A. Allan, MD, PhD, director, repetitive strain injury center; supervisor of occupational medicine, Presbyterian Medical Center of the University of Pennsylvania Health System, Philadelphia.