A drug used to build bone mass might help relieve arthritis pain.
A drug used to build bone mass might help relieve arthritis pain.

A medication that builds bone mass in patients with osteoporosis might actually help repair damaged joints and could be used to treat people suffering from arthritis, according to University of Rochester Medical Center researchers.

The study authors hope their findings, published in Science Translational Medicine, will lead to clinical trials to test human parathyroid hormone in arthritis patients.

Many older people suffer from arthritis, which is a painful joint condition. Treatment options have been very limited for some forms of the disease.

Osteoarthritis is the most common form of the disease. It occurs when cartilage breaks down, so it can no longer cushion bones as they move against each other in joints like the knee, hips, or hands.

The body maintains cartilage with parathyroid hormone (PTH). A synthetic form is used to treat the bone disease osteoporosis. It's called teriparatide, sold under the brand name Forteo. Researchers at the University of Rochester thought this osteoporosis drug might help rebuilt cartilage in arthritis patients.

To find out, Michael J. Zuscik and his colleagues used mice with injured knees, simulating arthritis. Some of the animals got the drug Forteo, while others did not.

"The treatment with Forteo induced the cartilage to become thicker by 32 or 35 percent relative to animals that were given a placebo treatment," Zuscik says.

Currently, osteoarthritis patients use a variety of medicines to treat pain, but available drugs do nothing to reverse the actual damage that causes the pain.

"In the context of human disease, this is what we would love to do. We would love to be able to take an arthritic patient, provide them with a therapy that actually makes their cartilage thicker, so they have longer lifetime use of their joint," Zuscik says.

The researcher says it wouldn't make the joint like new, but it would roll back the clock, so that the painfully arthritic knees of a 70-year-old might become more like the pretty-good knees of a 60-year-old.

More research is needed to see if Forteo would be effective in humans, and safe. Osteoporosis patients get a warning of one possible risk. Studies of Forteo in rats have found the drug increases the risk of a rare bone cancer, osteoscarcoma. But studies of other animals, including primates, have not confirmed the rat finding. Still, to be on the safe side, Forteo is not prescribed for people with a history of cancer.