Drugs that are used to treat osteoporosis may also help prevent the bone abnormalities that can lead to arthritis of the knee, new research suggests.

Alendronate (Fosamax) and estrogen seem to be most effective at halting the knee deterioration that can cause or aggravate osteoarthritis, says Dr. Laura Carbone, director of the metabolic bone unit at the University of Tennessee Health Science Center.

The Study

Carbone and her team of researchers evaluated 818 women who had an average age of 75.

Of that total, 214 women were taking either estrogen or Fosamax to prevent osteoporosis-related bone fractures.

When Carbone's team looked at the magnetic resonance imaging (MRI) results, women who were taking Fosamax or estrogen had significantly fewer bone abnormalities associated with severe knee arthritis than women taking other or no medicines.

Other osteoporosis drugs, such as raloxifene (Evista), risedronate (Actonel) and calcitonin spray, seemed to offer little, if any, change in knee arthritis.

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

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

The Connection

The researchers believe the osteoporosis drugs work by stopping the breakdown of the bones. "If you decrease bone breakdown, then hopefully the osteoarthritis won't be as severe," Carbone says.

"If we can thicken the bone, maybe we can alter the arthritic changes," adds Dr. Peter Bonutti, an orthopedic surgeon who performs knee replacements.

That's important, because knee arthritis is one of the five leading causes of disability in older men and women, according to the American Academy of Orthopaedic Surgeons (AAOS). It usually results after joints are injured, infected or traumatized.

It's too early to suggest that women take Fosamax to slow the progression of arthritis, Carbone says. "But if you have to take one of these drugs for osteoporosis, [Fosamax) may have some beneficial effect on osteoarthritis of the knee.

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