The off the bench (or step) squat: If you wish to progress more slowly then start on your stairs at home, this give you the added safety of the handrail for support. Stand on a bench or step that is knee height. Stand with the right leg parallel to the side of the bench and the left leg hovering in the air beside it. Keep the left toes level or higher than the left heel (foot flat). Raise your hands in front of you for balance and bend your right knee and slowly lower yourself. Think of it as trying to sit down while standing on one leg. Keep your back straight and look straight ahead, focus on a point ahead of you. Keep your chest up and ‘open’. Don’t lean your torso forward. Your knee should be over your second toe (the one next to the big toe) and shouldn’t travel further forward than your big toe. Be aware that your knee should be over your foot and not to the left or right of it. Lower yourself till you feel your balance go or your left foot touches the floor. Do not drop your left hip. It is to remain in line with your right hip. The aim is to squat not tilt. Sit back rather than lean forward, as if you are going to sit down.
Now raise yourself back up. Do not lock out the knee when it is straight; keep the knee ‘soft’. That is one repetition. Lower yourself on a count of 2 (if prescribed) and hold for 1 (if prescribed) and raise yourself for a count of 2 (if prescribed). Then switch to the other leg. Repeat the movement for the prescribed amount of repetitions.
See video here.