This has been a topic that people, including myself at one time, have misunderstood because of what professors or the typical trainers may say. The fact is that squatting below parallel is perfectly healthy for your knees. However, most people lack the necessary mobilities to squat this low and often times, at someone’s end range you will see a “dip” or curling under of their lumbar spine. This is the person hitting the end range in their hips and continuing to hit this end range (spinal flexion) is definitely a contributing factor to disc injuries.
In this video (thanks Kevin), even though it is demonstrating someone with a hip impingement, at the end range you notice the butt dipping under slightly. I have seen this in countless weight rooms and pushing through the hip end range can cause A LOT of problems.
In the Biomechanics of Squat Depth it shows that the highest forces on the ACL occur at 15-30 degrees of hip flexion while the lowest forces were at 60 degrees or more of hip flexion. So those quarter squats you see people doing, not so good, although there may be some certain situations where it may be applicable. The point is that, yes, not everyone needs to squat to parallel, especially if you do not have the necessary mobilities. A lot of people, are just not meant to squat. But it is a completely different story that people can say squatting “hurts” or is bad for their knees when there warm-up consists of shaking their arms around for 7 secs and touching their toes to pick up their NO-Explode drink. It is safer, for those individuals who are not meant to squat, to stay 2 inches higher than to cause some back problems later in their progress. However, it would seem foolish to say that deep squatting is bad for your knees for everyone.
What to do then if you cannot deep squat?
This is why I am a big advocate of single leg training because it usually allows the full range of motion without the back being the limiting factor.
- Reverse Lunges (dumbbell in each hand, Goblet position etc.)
- Rear Foot Elevated Split Squats (w/ dumbbells, or barbell in front squat grip, back squat grip)
- Even step-ups (bench has to be appropriate height)
For some awesome reads on this, check out these next few articles
Is It Wrong to Squat Like a Child– Craig Liebenson, DC
The Biomechanics of Squat Depth– Brad Schoenfeld
If you do not know how to properly warm-up, here is a quick one David Lasnier put up. He runs through it quickly to show a quick sample, but each movment is done 8x/side.