Strong thighs now could save your knees later.

RODALE NEWS, EMMAUS, PA—Suzanne Somers may have been on to something when she created the ThighMaster some 20 years ago—and, if she's been using it, she may be appreciating the benefits right about now. A study published in a recent issue of the journal Arthritis Care and Research finds that stronger thighs may reduce osteoarthritis of the knee, the most common disability in the United States, according to the American Academy of Orthopaedic Surgeons. The condition affects about 9 million Americans.

THE DETAILS: Researchers followed 3,695 adults between the ages of 50 and 79 who were free of both types of osteoarthritis of the knee at the start of the 30-month study. The two types are radiographic tibiofemoral osteoarthritis (symptom-free osteoarthritis diagnosed by an X-ray) and symptomatic whole-knee osteoarthritis (diagnosed by stiffness, aching, or pain in the knee joint). Each month, the participants' knee extensor strength (the strength of the four quadriceps muscles on the top of the thigh), was measured. By the end of the study, 10 percent of the women and 7 percent of the men had developed some form of knee osteoarthritis. Among those who didn't get it, knee extensor strength had the greatest protective affect against symptomatic osteoarthritis, though only in the women.

WHAT IT MEANS: Strengthening your thighs may save your knees, especially if you're a woman. Osteoarthritis of the knee is more common in women, anyway, so all women could stand to spend a few minutes each week strengthening their thighs. "You can't really strengthen your knees per se," says Selene Yeager, personal trainer and coauthor of Move a Little, Lose a Lot (Three Rivers Press, 2009). "But you can strengthen the muscles that support them and help your kneecaps track properly, which prevents a whole host of wear and tear," she adds, including osteoarthritis, which is also known as "wear-and-tear" arthritis. Stronger knee extensors have also been found to improve posture and balance, so you'll reduce your risk of osteoarthritis of the knee as well as your risk of falls as you age.