Myth #1: Squatting below parallel is bad for your knees
Despite the ability of the knee joint to provide an average of 140 degrees of flexion, the idea has been promoted that knee flexion should be limited to 90 degrees during a squat. This myth can be traced back, at least in part, to a single study published in 1961 by Dr. Karl Klein at the University of Texas. Dr. Klein determined that a group of competitive weightlifters displayed greater laxity at the knee joint than a group of non-lifters, and issued a blanket recommendation against squatting below parallel. The study was of very low quality, though, and Dr. Klein was seeking to validate his bias against squatting below parallel. Somehow, this erroneous belief was adopted by the general population and has remained standard dogma ever since, even though it’s been disproven many times over.
Powerlifters squatting double their body weight, to depths of 130 degrees of knee flexion, have been shown in studies to have more stable knee joints than individuals who do not squat. In fact, separate studies have revealed that the knees of those who regularly squat deep are more stable than distance runners and basketball players! In one study of female volleyball players, researchers concluded that there was no statistically significant increase in peak forces at the knee when squatting to depths of 70, 90, and 110 degrees of knee flexion. Yet another study showed that forces on the ACL are reduced as the knee is flexed beyond 60 degrees, and forces on the PCL are reduced as the knee flexes past 120 degrees. Still further studies show that powerlifters who are squatting over twice their body weight experience shearing forces on the knee that approximate only 25% of the maximal tensile strength of the ACL, and 50% of the maximum strength of the PCL.
Obviously, this doesn’t mean that just anyone should attempt to squat with a load equaling twice their body weight on their back. While those feats clearly demonstrate what the human knee is capable of, the important point is that forces on the knee are actually reduced as squatting depth progresses beyond parallel. How deep should you go, then? Well, once you are able to drop below parallel, meaning that the crease at the top of your hips is below the top of your knees, then you should only squat as deep as you can without losing form. If your lower back starts to round, that’s your stopping point. And if you can’t squat below parallel without rounding your lower back, then don’t increase the resistance until you can. It’s also worth mentioning that you should utilize a stance that allows you to squat between your legs and not on top of them, because pressing the hips directly against the calves under a heavy load can create a dislocating effect on the knee.
Squatting below parallel has the additional benefit of significantly increased activation of the gluteal muscles. The deeper you squat, the greater the glute activation. Whether you’re seeking to improve your performance or your appearance, you’re not doing yourself any favors by leaving the glutes out of the picture.
