Lying on your back, bend your knees keeping both feet flat on the ground.
Extend your left leg straight, keeping it raised about two inches from the ground.
Then, with your left leg extended, press through your right heel, lifting both hips off the ground. Make sure to keep your foot directly beneath the knee to protect the joint and continually press through the heel of the foot to lift the hips.
Slowly lower and repeat for 10 times before switching sides.