Botox May Reduce Knee Osteoarthritis Pain

Botox shots may do more than get rid of wrinkles. A new study shows Botox may decrease the pain of knee osteoarthritis (OA) and potentially prevent or forestall the need for knee replacement surgery.

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, M.D. 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.

Botox is a purified form of botulinum toxin type A and has been used to treat wrinkles and creases on the face. It is currently FDA-approved to treat other conditions including excessive sweating, eye disorders, and certain neurologic conditions. Botox is being studied for treatment of headache, ringing in the ears, overactive bladder, diabetic nerve pain, and more.

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 percent decrease in pain and a 25 percent 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."

The new findings came about when researchers noticed that people with limb weakness from a stroke or polio did not develop arthritis.

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.

Safe treatments are desperately needed for people with knee osteoarthritis.

"This is an exciting new approach to knee pain due to OA," she says. "Total joint replacement has been the single greatest advance for relieving the pain of OA, but not all patients are candidates."

Some people with knee osteoarthritis are too young for the surgery and others are too old. In addition, nonsteroidal anti-inflammatory drugs, which are commonly taken to relieve the pain of knee osteoarthritis, are not without risks, such as gastrointestinal problems and increased risk of heart attack or stroke. There are also risks from long-term use of opioid pain killers, including risk of addiction.

The Botox treatment seems to be extremely safe, she says.

Muscle weakness can occur when Botox shots are used to treat cervical dystonia, but such effects were not seen when the toxin was injected into the knee joint. "Since we are not injecting it into the muscle, we do not see any weakness to the limb," she says. "We use a very small dose and there are no significant adverse effects due to injection."

Shreyasee Amin, M.D., an assistant professor of medicine at the Mayo Clinic in Rochester, Minn., tells WebMD that "this is an intriguing finding and Botox could have a role in patients who have risk factors or contraindications to knee surgery. And if it doesn't have side effects to knee strength, it would be very helpful."

Robert L. Wortmann, M.D., professor and chairman of the department of rheumatology at the University of Oklahoma in Tulsa, agrees. "It's too early to say for sure what role injections of Botox may play in knee OA," he says. "But having the possibility of something that may alter the course or pain levels for a disease to which there is no known cure is really exciting."

He adds that "if it does have a positive effect in knee OA, it will likely have an effect in hip OA as well."

SOURCES: 70th annual meeting of the American College of Rheumatology, Washington, D.C., Nov. 10-15, 2006. Maren Mahowald, M.D., rheumatology section chief, Minneapolis Veteran's Affairs Medical Center; professor of medicine, University of Minnesota, Minneapolis. Robert L. Wortmann, M.D., professor and chairman, department of rheumatology, University of Oklahoma, Tulsa. Shreyasee Amin, M.D., assistant professor of medicine, Mayo Clinic, Rochester, Minn. WebMD Medical Reference provided in collaboration with The Cleveland Clinic: "Cosmetic Procedures: Botox."

By Denise Mann
Reviewed by Louise Chang, M.D