Most people have forgotten how to squat even though the squat is a natural movement for the body just like walking and running. The right way to squat is with your heels on the ground. That’s when you are stronger and you can lift more weight safely without insane stress on the connective tissues of the knees.
If you were to do heavy barbell squats with your heels off the ground and the weight on your toes, similar to a hindu squat, your knees would be destroyed in a matter of seconds.
The ligaments and the patella tendons would be the most likely victim.
The main reasons that cause lifting of the heels when you squat are: poor ankle flexibility and body awareness;
Truth be told most people have the ankle flexibility to perform correctly at least quarter squats, if not parallel squats. What’s actually stopping most lifters from doing the exercise correctly is usually the fact that they just don’t pay attention to what the body does. One of the best way to fix similar problems and increase awareness during squats is to perform wall squats.
The wall squat requires the lifter to face a wall at a very short distance. The lifter starts squatting while avoiding touching the wall with his knees and head. If you were to lift your ankles off the floor during wall squats, most likely your knees will touch the wall. The low is meant to act as a correctional reference.
In the beginning doing wall squat will feel weird and you will hit the wall with your head on the way down many times. Keep going as deep as your flexibility allows you to and overtime increase the range of motion (ROM). Before you know it you will be doing perfect low squats.
If your ankle flexibility is really bad, you can add additional ankle stretches to improve the flexibility of the calf muscles.
For a detailed explanation on wall squats consult the video below recorded by Shapeshifter Media: