People who suffer from arthritis pain in their knees may get longer-lasting relief and require fewer shots at the doctor's office. Scientists announced Wednesday that tiny particles called nanoparticles that they have developed can deliver pain medicine to the inside of the knee and keep it there longer. The study led by Michael Morgan of Bend Research has not yet been peer-reviewed, but he believes his work showed progress in pre-clinical trials.

This could be good news for the 30 million Americans who have osteoarthritis.

Morgan and his colleagues at Bend Research have been working on the particles for about five years. A nanoparticle is so small that it can only be seen with the help of an extremely powerful microscope. If humans shrank to the size of a nanoparticle each, the entire population of China would fit on the head of a pin.

Researchers said the nanoparticles do two things. Pain medication sticks to them, drugs then carried into the knee joint. The sphere-shaped particles also stay in the knee to slowly release pain medication.

If the nanoparticles work in humans as Morgan expects they will, patients would only have to get injections to manage their pain every few months instead of every week.

This is an area of great need - the ability to put something in the knee and keep it there, Morgan said.

Nanoparticles have been used in other parts of the body as little vehicles to deliver drugs, such as cancer treatments, but they have never been used in the knee. Morgan said particles used in the human knee would have to be even smaller than those used for other purposes so they don't cause inflammation.

Morgan's presentation was part of the American Association of Pharmaceutical Scientists meeting taking place this week in Washington, D.C.