My tibia and fibula were broken treated with orif. why does my leg feel so heavy?

Needs evaluation: It is hard to tell for sure what you mean by leg feels heavy, which can mean different things to different people. If you are having difficulty lifting your leg or foot, it could be a sign of nerve damage. There is a nerve close to the fibula which helps lift the foot and turn it out. If it isn't working properly it can result in "foot drop". Deconditioning can also give a "heavy" feeling.