I originally posted my query in a thread where someone had claimed low shoot the ducks (and, by implication, sit spins) were bad for one's knees, because they were too deep a knee bend.
I was merely trying to figure out whether the claim was considered to be universally correct, or whether it just applied to people with certain types of knee (or back?) injury.
I do have a knee problem: My knee caps move a bit side to side, creating pain and potentially wearing cartilage, as I rise up from one leg knee bends and raises (e.g., shoot the ducks). This occurs (says a PT) because I am trying to do it all with my quad (the big leg muscles are in front of the knee), instead of properly involving the many other muscles which stabilize the kneecap position (e.g., psoas, obliques, abdominals, lower back muscles, gluteous family muscles, in fact the entire hip flexor family, etc.), by pulling at a variety of angles from all sides, as he says most people do. (In addition, insufficient use of those muscles leaves them cold, so they can't stretch, which severely limits forward bend, back bend, wide leg stance flexibility.) Knee bends and raises, lunges, and sitting in full squats, as well as leg raises in many different directions, are part of the exercise regimen the PT advocated to fix it, so I guess he doesn't believe bending the knee is bad - for me.
He blames a lot of health problems on all the time many of us sit in western style chairs, which only place tension on the quads, and leave us long-term in one body position: he thinks squatting positions, which of course involve very low knee bends, help keep people in other cultures healthy, because more muscles are involved, and that we should also use a wider variety of chair styles to exercise and stretch more parts of the body.