I just want to point out the importance of avoiding uneven knee compression.
Anyone who's read Mark Rippetoe's Starting Strength knows what I'm talking about, he goes over it in the squat section.
When crouched, and your knees are bent (yes, past 90), make sure they're in line with your toes.
If you keep your toes pointed forward, facing straight infront of you, make sure your knees are doing the same, and are in line with them.
If they point out ward, and form an angle, make sure your knees point out in the same direction. Like I said, if you don't, you'll be putting too much uneven compression the outside or inside (depending on how you land) of your knees.
If, when you look down at your toes upon landing, and they're like this:
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, then make sure your knees point forward with them.
If they look more like this:
\ /
, Make sure your knees point the same way as your toes.
The knees and toes should be vertically in line together.
PS: Landing, but not allowing your knees to bend past 90 means you have to finish the landing by bending over a lot at the hip, and I'm sure your legs can bear the brunt of the landing way better than your spine and hips can, since your knees flex and more fluidly compress into it, while bending at the hip means you have to arc your back way too much.