This exercise increases the strength of the external rotators of the hip.
To do this exercise you will need a mat and a soft ball. Start by lying on your side with your knees bent and your heels lined up with your pelvis. Your bottom hip will be on top of the soft ball. Inhale into the back of your ribcage and then exhale as you externally rotate to top leg to lift the knee. Inhale as you maintain the external rotation and exhale again as you lift the knee into the air. Repeat 8-10 of these leg lifts.
Things to think about
Imagine the connection of your thighbone to the hip socket. In external rotation the hip is the most congruent and connected. This exercise can help release and build strength in the leg that protects the knees.
Be sure that your hips are stacked. This will allow your body to find external rotation, but if you allow your hip to roll back then the quadriceps and other muscles will be recruited.