Here's the link to my video describing my theory about how to train to improve vertical leap, and exactly how I do it in my small apartment.
If you do heavy dead lifts at home that has a yard, you can use my technique and drop the barbell at the top of the lift on the grass/ground/sand. It would be nice if some younger guy's on this forum to try my technique for a few months and see what happens.
http://www.youtube.com/watch?v=vFWLLTa1Qdw
solid presentation on that video.
the exercise itself looks decent but awkward -> same leg/same arm seems awkward to me. i feel like using opposite arm/leg might feel a bit more stable and allow you to get a "better" angle on the "single leg squat" while holding the db right underneath you. have you tried that? if so: like or dislike it?
if i didn't have barbells/rack etc, i imagine that exercise would have some effectiveness. i'd personally do other stuff as well, not just that exercise.
i did single arm db exercises and found them effective (sl db squat, sl db rdl, sl db bench), but I never did those variations "concentric only" with a drop.
hope your knee is ok.
pc!