> "It is important however that your knee isn't bent at more
>than a 90 degree angle."
>
>Why is this? It it stress on the knee, or something else? I
>ask because I am almost 4'11", and do leg press on 14". I
>actually dip down on my landing leg then quickly lift it to
>make the press deeper for the working leg, because I am still
>using the Fanny Lifter which is only 14".
Yes, having a tighter than 90-degree angle in the knee when it is loaded (bearing weight) is tough on the joint. You may not have had problems yet, but it is also something that may not show up immediately, or you could be lucky and never have problems. It is, however, a higher risk technique and there is more chance of injury. I suggest that, instead of continuing to take the risk, you decrease your step height. You can still do the dip down, but if you make sure that your leg is at a 90-degree angle or more open when you are not dipping down, then you will be safe.
I use this "dip" myself, as it allows me to somewhat pre-activate the glutes (as I rise from the dip to the regular starting position, I make sure to put pressure through my heel to activate the glute/hamstring area). When I am standing normally behind the high step, my knee is more open than 90-degrees.