Lying on your side with knees bent and feet and knees together. Support your head with your bottom hand and use the top hand for support.
Lift the top knee away from the bottom but keep the feet touching.
Hold at the top and then slowly lower. Ensure that you do not rock backwards at all (which means that you will probably not need to lift your knee as high as you think you do).
Your goal is to complete 15-20 reps with relative ease. Build up to this gradually. When you can complete these then add some resistance using a mini band.