A Swedish ergonomics expert has developed a new type of mouse which, he says, won't cause some types of repetitive strain injury.

The Ullman Mouse, named after its inventor Dr Johan Ullman, looks like a joystick. But looks can be deceptive. The stick protruding from the top of the mouse (pictured) is used to propel it around the desk and, because it is held like a pen, says Ullman, it won't cause injuries like normal mice.

By using it like a pen, muscles in the forearm and upper arm are at rest and the user's hand and forearm are in a more natural position, rather than being twisted around horizontally, as they are when a mouse is used.

It's this position which causes mouse arm syndrome, a type of RSI that affects millions - a figure which includes half of the Swedish population, according to Ullman.

"When you use a mouse you use these muscles," he said, pointing to his upper arm. "These are made for chopping wood and hitting people in the face, not for precision work. That should be done with your arm resting and these [upper arm] muscles resting and then you can do precision work."

The mouse, which has an optical pick up, can be pushed effortlessly around the computer desktop without users needing to lift or move their arms. It also helps the user keep more control over the mouse, Ullman said, and even allows users to sign their names with it.

He set about inventing the new mouse two years ago. "I'm a medical doctor and I've had hundreds of patients with these problems," he said.

"One day I suddenly realised that everybody has missed something here. This is high-precision fine motor work that is being performed with large motor muscles, and that can never lead to anything but problems."

The new mouse isn't available yet. Ullman is currently in talks with several potential partners, one of which is a major global PC maker, and hopes to sign one or two partnerships that will lead to commercial production, possibly as early as this year.