because poser's basic "bend" parameters only cover thefocal point and then a decreasing amount out in the actual surface area, this issue is one that pretty much plagues poser dramatically. It can be fixed. It requires additional joints in the areas being bent, to make it a "smoother" bend. When folks talk about how "bad" poser's rigging system is, what they are really usually saying is the default one and the Vicki/Mike one, both of which are fairly simple rigs, are bad for these sorts of works. A more advanced rigging has occasionally been tried, but they are not always successful commercially. I've long believed that if someone does do a more advanced rigging on a pleasing figure model, and then supports that model with adequate clothing, that they could change the way that sort of thing works. 3 bones for the knees and elbows, btw...

thou and I, my friend, can, in the most flunkey world, make, each of us, one non-flunkey, one hero, if we like: that will be two heroes to begin with. (Carlyle)