In one sentence, describe what the following article is about:

Stand with your legs shoulder-width apart. Keeping your legs straight, reach for your right foot. Hold this position for ten seconds. Then reach for your left foot and hold this position for ten seconds. Finally, reach toward the center and hold this position for ten seconds. Sit in a chair with your knees bent. Place your hands on the sides of the seat. Straighten the leg with the affected knee until your heel is resting on the floor. Keeping your leg straight, gradually lift it off of the ground. Lift your leg as high as you can. Then gradually bring your leg back down to the resting position. Practice one set of five to ten repetitions, four to five times per week. Place a mat on the floor. Lie on your stomach with your legs straight. Bend your arms and place them underneath your chest. Slowly bend the affected knee. Bend your knee as far as you can. Then slowly bring your leg back down to a straight position. Do three sets of five to ten repetitions. Practice this four to five times per week. Stand in front of a chair. Place your foot with the affected knee on the seat of the chair. Keep your standing leg straight. Move the foot of the standing leg back until your knee is bent at a 95 to 100 degree angle. Gradually lean forward. As you lean forward push into your knee. Then gently push back to the starting position. Do a set of five to ten repetitions. Practice this four to five times per week.
Stretch your legs. Try a sitting knee straightening exercise. Do an active knee bend. Try a step up lunge.