… your heels off the floor, rising up onto your toes. Hold, then slowly lower.
Straight-Leg Raises
Sit with your back against a wall, left leg straight and right leg bent with your foot flat on the floor. Slowly raise your left leg straight up about 12 inches off the floor. Hold, then slowly lower. Repeat with your right leg.
Short-Arc Knee Extensions
In the same starting position as the straight-leg raises, put a ball (about the size of a basketball) under your left knee so that your leg is bent. Slowly straighten your leg. Hold, then slowly lower. Repeat with your right leg.
Hamstring Stretch
Lie on your back with your left leg flat on the floor. Loop a towel or rope around your right foot and pull your leg as far as comfortable toward your chest, while keeping a slight bend at the knee. Keep your back pressed to the floor throughout the stretch. Hold for 10 to 30 seconds and then release. Repeat three or four times with each leg. Do this stretch five or six times a week.
Worst Exercises—Avoid These
A few of the following exercises can be done safely if you have chronic knee problems; they’re on this list because they’re more likely to be done improperly. The exercises above are safer, while still giving you similar results.
Full-arc knee extensions
Lunges
Deep squats
Hurdler’s stretches