Oh no, I'm sorry to hear her leg is giving her trouble. Unfortunately, that can be another sign of MBD. Bones can become deformed or fractured from calcium deficiency, though since you said it felt firm, this may have occurred in the past and is hopefully only a lingering disfigurement. Here is a link with other signs of MBD: PetMD

Keep in mind that when you do take her to a vet, they might want to do blood tests or x-rays, so her bill might be hefty. If anything, hopefully they can just feel her bones to see how strong they are and maybe do a blood test just to be sure. Until then, just keep dusting her tasty food! Packie is very lucky she got an owner who cares so much.