Swaying arms (for a zombie)

Hello all!

I have a humanoid character that’s been fully rigged. I would like to know, is there a way that I can have the arms of the skeleton be affected by physics (much like a ragdoll), while the rest of him walks/moves? The premise is to make a zombie that has a shambling animation. I’d rather have the arms be controlled by simple rigid body physics, while I animate the rest of him.

Thank you!