I'm not sure of the cause yet, but the fix is fairly easy.
After you've run TSM Rigger*, open up the model's Bones folder in the PWS and select "body" at the very top.
Hit the * key on the number pad once or twice to expand out the entire skeleton tree.
scroll down to find this area for the back leg:
Click to view attachment
I've noted the three problem bones with red arrows.
If you select one in the PWS, and look at the model from the top you will see its roll handle is pointing off to the side:
Click to view attachment
You could try to turn it forward from the top view but you can get it more exactly aligned by dragging the roll handle in the side view:
Click to view attachment
Do this for all three bones. Select one in the PWS, then fix the roll handle in the model window.
Do this also for the analogous bones in the "left" back quad leg.
Do I need to tell you to be careful not to accidentally select some other bone when you're stabbing for that roll handle?
Well, I will.Save your model again.
Do I need to tell you to save it under a new name just in case you didn't do this quite right and you need to try again with your "unfixed" model? Well, I will.
Now the TSM constraints should no longer cause the leg to twist when they are on.
This procedure is for a quad leg that is generally oriented like a horse's or dog's leg; a leg that goes down from the body. I haven't tried this on something like an alligator leg that is modeled out to the side. When some one comes up with a case like that I will be interested in seeing what happens.
*I always save the model after I've run TSM Rigger, then restart A:M and reload the model. This gets rid of most of the "string errors" that are written into the names of some of the constraints. They don't affect the operation of TSM2 but they were messy to look at.
