People suffering from painful arthritic knees may soon have a new therapy to turn to: sugar water.

In a new study published in the Annals of Family Medicine, researchers from the University of Wisconsin School of Medicine and Public Health and the University of Iowa reported their investigation of dextrose prolotherapy: injections of sugar water to the site of pain in the knees of people with osteoarthritis. The team recruited 90 adults between the ages of 40 and 76, who had gone through at least three months of painful knee osteoarthritis, and either assigned them to do at-home exercises or injected them with the dextrose prolotherapy or with saline solution.

They found that the patients who received sugar water injections had significantly less pain and were very satisfied with their therapy. "Prolotherapy resulted in clinically meaningful sustained improvement of pain, function, and stiffness scores for knee osteoarthritis compared with blinded saline injections and at-home exercises," the team wrote.

Prolotherapy involves small amounts of a solution being injected in multiple places in a painful ligament, Reuters says. The idea behind it is to create a minor irritation in the ligament to prompt the body to heal the damage, and hopefully the damage from arthritis along with it. The therapy can cost between $200 and $1,000 a session and isn't currently covered by Medicare, Reuters adds.

There have been previous studies done on the efficacy of prolotherapy, but this study seems to have produced the most reliable results, University of Washington pain specialist John Loeser told Reuters. "This is a well-performed clinical trial that deals with many of the issues that have clouded prior reports of prolotherapy," said Loeser, who was not involved in this study.

However, there are still questions that need to be answered before prolotherapy becomes the standard treatment for people with osteoarthritic knees, he added. For example, the study followed patients for only one year after their treatment, so it is not yet known if the effects last more than a year, Reuters says.

The study's first author, David Rabago, M.D., told Reuters that he believes the study's results support the use of prolotherapy as a treatment for patients who haven't had any luck with more conventional treatments. Although all the details of how the therapy works and how long it lasts are currently unknown, Rabago told Reuters he'd be comfortable recommending prolotherapy to members of his own family.

Source: Rabago D, Patterson JJ, Mundt M, et al. Dextrose Prolotherapy for Knee Osteoarthritis: A Randomized Controlled Trial. Annals of Family Medicine. 2013.