The preliminary research was presented at the 2006 annual meeting of the American College of Rheumatology.
Injecting Botox directly into the knee joint relieved pain and improved function among people with severe knee osteoarthritis after one month, says researcher Maren Mahowald, MD. She is the rheumatology section chief at the Minneapolis Veteran’s Affairs Medical Center and professor of medicine at the University of Minnesota in Minneapolis. Mahowald now plans to evaluate the participants after three and six months.
The new study comprised 37 people with moderate and severe knee osteoarthritis. Participants received 100 units of Botox with the anesthetic lidocaine or a dummy injection with lidocaine directly into their knee joints.
After one month, people with severe pain showed a 28% decrease in pain and a 25% improvement in function. By contrast, people with severe knee pain who received a placebo did not show a significant decrease in pain.
Botox injections had almost no effect among people with moderate pain, the study found.
But it’s still early, Mahowald points out. ”Patients often have continued decreases in pain and improvements in function after one to two months. And I think there will be more improvements at the three-month evaluation.”
Exactly how long the effect lasts will be determined at the six-month evaluation, she says. “People may require one to three injections per year to control knee pain, but these injections may obviate the need for knee surgery.”
They also noticed that when people with cervical dystonia -- neck muscle stiffness and spasms -- received shots of Botox, their pain improved before their muscle contractions stopped, suggesting that Botox may have a soothing effect on pain nerves.