In this example I have an elbow, which is best described as a 7 sided cylinder with a level 2 subsurf on top.
I rotate the forearm 90 degrees and it twists up and does a spindly shrink thing.
Without using shapekey’s and drivers, what is the best way of modelling to avoid this?
Cheers!
i’m not sure if i got what you want
but
i simply would use extrusion
What? This is the rigging forum yes?
yes it is
is there already a bone attached to the arm??
Yes, an upper arm and a forearm, jointed in the elbow.
It’s the forearm which has been rotated 90 degrees.
ah…okay did you check it in the weight paint mode?(there you can select wich character parts are influenced by the bone)
would be easier to help you with the .blend 
My hat off to you! Thankyou…
Hey dude,
If you select one of the bones on edit mode, go to “BONE” on the areas options on your left, you will find a option called “Curved Bones”, Change the segments to 5 or 6, and "Easy in Easy out’’ to zero.
go ahead and do your animation again, i think it will works.
I case you have a lot of troubles on rigging, i must say that on blender cookie.com there is a good tutorial thar teaches about this. Here is the link:
Hope it helps you 
I’ve done that tutorial, that’s why I started using bbones, I also set the segments, must have mised the ease-in / ease-out bit…
This is the answer i’m looking for! Cheers…
UPDATE:
I’ve just tried this newer way on a proper model, and it works great, but in certain positions it happens again.
Applying the previous method works on it’s own in all positions, even though currently i’ve got it applied over too large an area so it’s adding curvature, but I can localise that…