Stretches For Bad Knees: Partial Squats
Partial squats are for those who cannot fully squat due to limitations already exhibited by the knee or a lack of mobility in the hips or ankles.
If you have bad knees, you may want to steer clear of deep squats. Poor form and muscular imbalance can make this movement risky. However, a partial squat can strengthen your knees. Keep your knees over or behind your toes and your belly button pulling in and up towards your spine. For good measure, place a chair beneath you and pretend like you’re going to sit down — but don’t. This will keep you from descending into your squat too far.
However it is important to note that once you have strengthened your knees, it is beneficial to revert to full squats.