Regarding the analysis of the knee position during the box jump test in a functional movement screen/prehab test, what exactly does it mean if the knee bows in or out?
Bows out is nothing to worry about.
Bows in is poor control of the natural femoral internal rotation that comes with any stance. Gravity wants to take the femur into internal rotation by the natural vectors and resultants on the human body; it is the same for everybody. The box drop that you describe challenges not necessarily strength, but neuromuscular control. Different pundits call it different things, but it is basically the lag time or on/off mechanism that the brain engages in to use the right muscles to meet a serious challenge. As the hip is not resisted against internal rotation, the tibia meets it with external rotation, and the knee falls into a valgus position, but it’s really more a function of transverse action looking like and creating a frontal action. Poor landing mechanics as you describe is simply poor neuromuscular control. This a generic answer for actually a similarly vague question.
If the knee bows in, does it mean that the athlete has tight adductors and weak glute meds?
It can mean either of those, both, or any other combination of poor mechanics somewhere else. Theoretically any poor dynamic posture in the body can cause knee valgus.
If the knee bows out does it mean the athlete has healthy hips or does it mean that the athlete has an overactive muscle group in the hip region?
True knee varus is usually a structural issue that can not be addressed physically. It is an orthopedic issue as far as I know, but I do not see it often. Tinkering with the hip with coxa valga is a physical means to address genu varum.
- Knees pushed out is solid squat/jump/land mechanics. It is what is supposed to happen.
- I don’t think you can have too much ER in squat, step, or lunge mechanics unless you supinate so much that the sesamoid of the big toe comes off the ground. Now you are taking it too far.
- Keep in mind the athletic ready position is not the same as the squat position. The agility training position looks like a bad squat, but stability of the hip and knee is a premise of control, not a maximal end range hold.