Bees do in point of fact have knees. And their knees do please in a way, appropriately nifty with respect to this expression. For the knees of the bees (on its hind legs at least) form what is called the pollen basket. That is where the bee carries the bits of pollen which it borrows from flowers, with tiny hairs on it's legs aiding it in holding steady to a gathered clump of the substance as it wends its way to its home hive. So the knees of the bees keep the pollen from a-fallin' so the bees can make some honey. Which we'll pay for. With our money.

And, naturally, as the bee wends its way home with this precious cargo, it will stop at a few other flowers to pick up a bit more here and a bit more there -- and as it does, its knees will fall a wee bit short of the task, dropping some of its pollen from this or that flower onto a one of the flower's mates -- and, presto, pollenization!!

Delightful as these posterior limb-type implements are, it remains a mystery whence came the expression of something grand being 'the bees knees.' It may well have come from nothing more than one dawdler's word-play catching on. But some speculation points to the expression being an abbreviation of sorts, a shortened form of 'B's and E's,' in turn derived from 'beginnings and endings' (the English translation of the much more ancient 'Alpha and Omega') or 'be alls and end alls.'