Which Squats for Which Knee Issues???
Not all squats are the same and not all squats have to be full range depth.
Should you be able to squat in every position? Yes. Should you be able to handle a large load overhead? Yes. Did you build a front squat back squat? Of course.
The box squat forces us to have pause and exert concentric control.
The foot pressure gives us a chance to pause and it forces athletes to be able to control their range at a certain depth. So if there's a range where there's pain, or if we're trying to eliminate exposure or minimize risk of a certain depth or forward translation of the knee then the box squat can give us some some feedback about the depth and can put us in a place where we can concentrically stop, pause, and not bounce to get out of the bottom position.
One of the reasons we love the box squat is that if we're trying to have someone control the shin (which is where we see a lot of knee pathology or pain related to squatting where someone's had an acl tear and we're trying to protect that graft) while still getting them squatting and rebuild that neuromuscular program we do tend to try to keep the shin a little more vertical.
We can use the hamstrings as a way mechanism of keeping the shin upright instead of having that shin run forward which is a way of basically unloading and protecting that ACL.
Tibia coming forward where it starts to introduce more sort of dynamic loads to the knee which are harder to manage.
We can get athletes to keep a pretty verticalized shin while squatting. The key here is that we're also interested in the control coming back up. If someone has knee pain or history of patellar tendinopathy we can get really simplified motion under control with tempo and then the reversal is them standing back up and having control of that hamstring just like when we hit apex on a swing.
If you have a person with knee history problems or pain in the knee - one of the things you can do is let that torso come forward and really control the shin angle and in this situation the box squat is a great idea. It allows us to really end up controlling the shin and keep that shin vertical which is one of the ways to manage some of the shear forces and which are potentially irritating or we're trying to rehab or protect or minimize that shear.