I've seen a couple of things which seem transferable to Poser, but I'd worry a little about the extra complexity and what it might do to posing and rendering. Poser still has some serious internal problems, it seems. Anyway, the simple answer might be to have a zero pose which is bent. So a straight elbow has a bend value of -20. I suspect it wouldn't make much difference to a human elbow, but it might make a significant difference to conforming clothing. More complicated would be an extra bone, not between existing bones as the V3 buttock is, but a spur which controls some of the elbow (or kneecap) mesh, and is driven by the motion of the main joint. Throw in magnets, and you maybe could set up something horribly complicated whixch would work in Poser, and fall apart at the slightest alteration.