This mainly stretches your buttocks (gluteal muscles) but also makes some demands on your groin and upper inner-thigh area. You must be very careful not to apply any stress to the knee joint when performing this stretch. Otherwise, serious injury (such as the tearing of cartilage) may occur.
Lie on your back again with both knees bent and in the air and with your feet on the floor. Take your right foot in your left hand (with your hand wrapping under your foot so that the fingertips are on its outside edge) and hold your leg (with your knee bent) in the air about 1-3 feet above your left breast (relax, we haven't started to stretch the buttocks just yet). The leg you are holding should be in much the same position as it is when you start your groin stretch in the next exercise, only now it is in the air because you are on your back (see section groin and inner-thigh stretch). Exhale and slowly pull your foot over to the side and up (toward your head) as if you were trying to touch your outstretched leg about 12 inches to the outside of your left shoulder. You should feel a good stretch in your buttocks about now. If you feel any stress at all on your knee then stop at once. You are probably pulling "up" too much and not enough to the side. You may wish to use your free hand to support your knee in some way. Hold this stretch for about 20 seconds (and stop if you feel any stress in the knee joint). Now repeat this same stretch with the other leg (using the other hand). Remember that the leg you are not holding should have the sole of its foot on the floor with the knee bent and in the air.
To make an isometric stretch out of this, when you are performing the passive stretch (above) and feel the stretch in your buttocks, continue trying to pull your foot to the outside of your shoulder while at the same time resisting with your leg so that it pushes agains your hand. No actual leg motion should take place, just the resistance. Stop immediately if you feel any undue stress to your knee.