Hm, but if you have specialized forms, could you, if you have a broken left arm, design a form that only has a right arm, and when you transform, tada, no broken arm?
Course, then we have the question, if you have a broken left arm and then transform into a four-armed two-legged creature, how many arms are broken? If one, could you then design a three-armed variant of that form that's missing the arm that would be broken. But if that worked, you'd just be able to remove another arm, then rearrange the arms so that you had two unbroken arms.
Probably the best solution would be to declare you always have the injuries no matter what the form, just on the closest piece of anatomy. So in the case of disappearing the arm that was broken, you'd have a broken shoulder until transformed back. Magibabble it as forms requiring a base stable anatomy to transform, and any disruption to the starting anatomy will result in a disruption in the resulting form.
