Fosamax and osteoarthritis

Osteoarthritis is the most common type of arthritis in the U.S. It causes the breakdown of cartilage between joints. Knee osteoarthritis is common and disabling in many older adults, causing pain, inflammation, and limited joint movement.

In osteoporosis, bones become progressively thin and porous, leading to an increased risk of fracture. It affects more women than men, since women typically have smaller and lighter bones. Women also lose bone mass at an earlier age and more quickly than men.

Medications to prevent or treat osteoporosis include Fosamax, Evista, and estrogen. They work by altering the cycle of bone formation and breakdown.

Taking Fosamax or estrogen for osteoporosis may help protect against knee osteoarthritis, according to a new study. Drugs used to treat osteoporosis may also help prevent the bone abnormalities that can lead to arthritis of the knee, new research suggests.

The study appears in the November issue of Arthritis & Rheumatism. (Carbone, L., et al. Arthritis & Rheumatism, November 2004; vol 50: pp 3516-3525.)

A team led by Dr. Laura Carbone, director of the metabolic bone unit at the University of Tennessee Health Science Center, evaluated 818 women, average age 75, enrolled in the Health, Aging, and Body Composition Study, a long-term look at factors contributing to disability. The ongoing research is being conducted at the University of Tennessee and the University of Pittsburgh.

Participants rated their knee pain and had MRI images and X-rays taken of their knees. Once a year, they also brought in all of their medications -- including over-the-counter drugs and supplements -- for the researchers to record.

"Women taking estrogen and alendronate had less MRI [magnetic resonance imaging] changes of severe osteoarthritis of the knee," Carbone said.

Osteoarthritis of the knee is one of the five leading causes of disability in older men and women, according to the American Academy of Orthopaedic Surgeons. The risk of disability from knee arthritis is as great as that from heart disease. Arthritis in the knee usually happens in joints that have been injured, infected or traumatized.

About 26% of the women were using osteoporosis drugs, including 125 on estrogen, 31 on Fosamax, and eight on Evista. Estrogen had been used for the longest period of time: almost 14 years, on average, compared to a little less than two years for Fosamax and Evista use.

Compared with participants who weren't taking osteoporosis medications, users of Fosamax and estrogen had fewer osteoarthritis bone abnormalities in their knees, according to the MRI images. Fosamax, but not estrogen, was also associated with reduced knee pain.

"Our study suggests that [Fosamax] and estrogen may protect against the development of bone abnormalities associated with knee osteoarthritis, which may have a beneficial effect on the overall course of the disease," write the researchers in the November issue of the journal Arthritis & Rheumatism. Carbone, Because few black women in the study took osteoporosis medications, the researchers can't promise that the same results apply to that population. They also note that the relatively short-term use of Fosamax and Evista might have an impact on the results of their study. They say that longer studies are needed to evaluate the potential of using these drugs to treat or prevent osteoarthritis.

"Different relationships might be observed if the drugs had been taken for longer periods of time," they write, calling for further studies on the topic.

Other drugs are available to prevent fractures, Carbone said, including risedronate (Actonel) and calcitonin spray. However, estrogen and Fosamax happened to be the ones most of the women in the study used.

When Carbone's team looked at the MRI results, women taking Fosamax or estrogen had significantly fewer bone abnormalities associated with severe knee arthritis than those not taking these medicines.

"Some [other] studies have looked at estrogen and osteoarthritis," Carbone said. "Some have shown an effect, and some have not."

Women taking Fosamax also had less knee pain than nonusers. "It's not like a painkiller," Carbone said. "But, long term, they may have less severe changes of osteoarthritis of the knee."

Exactly how do the osteoporosis drugs work? "What we think is, they stop bone from being broken down. If you decrease bone breakdown, then hopefully the osteoarthritis won't be as severe," Carbone said.

In the United States, Carbone said, about 1.5 million osteoporosis-related fractures occur each year. And osteoarthritis, also called "wear-and-tear" arthritis, is the most common type.

Another expert, Dr. Peter Bonutti, an orthopedic surgeon who performs knee replacements, said the study is interesting. "If we can thicken the bone, maybe we can alter the arthritic changes," he said.

The type of bone that benefited from the osteoporosis drugs in the study, called the subchondral plate, lies under cartilage, Bonutti said. It's subject to stress fractures, and once that occurs, pain can start.

It's too early to suggest that women take the bone-building drugs to slow the progression of arthritis, Carbone said. "But if you happen to have to take one of these drugs for osteoporosis, it may have some beneficial effect on osteoarthritis of the knee."

Carbone added she would like to do a longitudinal study in which she follows people over time, assigning some to take the drugs and some not. "This study is a cross-sectional study, one snapshot in time," she said.

Meanwhile, experts say you can do your bones a favor by getting regular exercise to strengthen muscles, tendons, and ligaments that surround knee joints. They also recommend maintaining a normal healthy weight and getting enough calcium (1,200 mg per day) and vitamin D for bone strength.

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