Al Roker and Oprah have both had total knee replacements (TKRs)— along with around 790,000 other people who undergo the procedure annually in the U.S. That's a lot of hospital and recovery time, and expense.

A new study now reveals an effective way to prevent or delay the need for TKR.

Researchers analyzed the legs of 134 people with knee osteoarthritis and found that those who had the strongest quadriceps (a four-muscle group on the front of the thigh) were 82% less likely to go on to have TKR.

They recommend that everyone with knee arthritis adopt quad-strengthening exercises to balance the forces that the quad and hamstring muscles exert on the knee and protect the joint from strain. Making sure your quads are strong before you develop osteoarthritis is a great preventive measure too.

To strengthen your quads safely, try these exercises:

• Seated leg lift. Sitting in a chair, with or without a resistance band around your ankles, lift one leg slowly as high as you can. Hold 6 seconds. Repeat with the other leg. 

• Mini squat. Holding the back of a chair, feet a shoulder's width apart, bend knees into a small squat at less than a right angle. Hold 6 seconds. Rise slowly. Repeat.

• Stair steps: Place one foot on the first step, slowly bring up your second one and then slowly lower it back to the floor. Use a handrail if needed. Repeat for 60 seconds. Switch legs. Walking slowly up and down stairs builds strength as well.