Quad sets are exercises to strengthen your quad muscles...

the muscles at the front of your thigh that help straighten your knee.

Here's how to do them.

Sit or lie down on the floor or a firm bed and straighten one leg.

Put a small, rolled-up towel under your knee.

Your other leg should be bent, with your foot flat on the floor.

Tighten your thigh muscles... your quads... in your straight leg by pressing the back of your knee down into the towel.

Hold this position for about 6 seconds, and then rest for up to 10 seconds.

Do this exercise 8 to 12 times on one side.

Then, switch legs and do the exercise 8 to 12 times on the other side.

Some soreness or discomfort may be expected...

but stop doing an exercise if you have increased pain.