One of the things I really like about Anime Studio is the way it deals with it's bone rigs. They are very straightforward (unlike ToonBoom -- don't get me started on pegs) and generally very easy to setup and use.
One thing that is a little difficult, however, is controlling the bend of a limb. The good news is there is a fairly easy and extremely effective way around this, and it's an approach that many animators use.
Rather than try and describe it in words, I thought I'd post a video tutorial (my first, and done in one take although with an edit here or there) to demonstrate how to set this up. While it might look a little involved trust me that once you've done it once or twice the whole thing takes less than five minutes to do. And then you're left with a very effective looking arm or leg.
Thanks to Genete for his bone rig and Vern for explaining to me how to use it (and possibly modifying it). If you want to download it you can do it here: