“Locked” Knees in the Squat

by Mark Rippetoe | March 02, 2021

One of the things we occasionally see is the tendency to leave the knees in slight flexion at the top of the squat. I think this probably comes from either the incorrect impression that locking out the knees is bad for the joints, or that it's better to remain in some flexion to more fully work the quads. Either way, it has to be fixed.

Fully extended knees is the normal anatomical position for the knees in a standing position. We stand erect with extended knees, so that the bones of the leg can support the weight above them while the muscles that control the knee angle rest. Any degree of knee flexion must be controlled by the action of the knee extensors – the quadriceps. When you squat down, the knee extensors control the closing knee angle eccentrically, when you stand up they concentrically contract to open the knee angle, and if you stand with your knees unlocked at the top they work isometrically to hold the position.

Perhaps the thinking is that the quads get extra work if you keep them in contraction at the top between reps. This comes from the time-under-tension people. I'd rather see them get extra work by squatting 5 more pounds than they did last workout, since getting stronger is our purpose in the weight room.

Or perhaps the thinking is that it's bad to lock out the knees under a load, when the reality is that it's normal to rest between reps at the top with locked-out knees. There is nothing about a fully extended knee under an load that can be squatted below parallel that damages the knees in any way whatsoever. The only damaging thing about a knee extension would be slamming into it forcefully to the extent of the range of motion the knee ligaments will allow. This is bad. Don't do this. It will hurt you. Just stand up, like you normally do anyway.

Some people have loose knees, and elbows and shoulders and hips and spines. Hyper-mobile joints can be a problem for the few people cursed with excessive “flexibility,” since an overextended joint can be placed in a position that injures it. I don't understand why the emphasis on “mobility” is so popular, since attempting to place a joint into a position outside its normal anatomical range of motion is both unnecessary and potentially damaging to joint stability.

But when you're squatting, just finish standing up normally. Don't slam into extension, and don't stay 5 degrees away from lockout. Just stand all the way up.