If you have been in a bad accident, and you have lost the ability to move parts of your body, physical therapy is definitely in your immediate future. The only way that you would not have to go through physical therapy is if you choose to refuse it. Additionally, your doctor may be more focused on a "functional restoration program" than on a full recovery. Here are the differences between these two approaches, and why you can choose to reach beyond just functional.
What Functional Restoration Means under These Circumstances
When you cannot walk or move your arms and shoulders, your doctor does not know the full extent of your injuries. He/she may be erring on the side of caution when he/she discusses a "functional restoration" with you. What this means is that he/she is looking at a rehab program that will slowly help restore feeling and movement in the parts of your body that are not currently able to move. Your doctor expects that you will be able to feel and move somewhat over time, if you are willing to work through this particular program.
Ultimately, however, it is up to you to decide if "functional" without a lot of pain and just enough movement is enough of a recovery for you. You may decide that you want a full recovery, or as close to a full recovery as you can get. If that is the case, you have to go through the functional rehab program first, and then ask your doctor to allow you to increase intensity and conditioning movements to reach the best possible outcome beyond just functional.
Beyond functional means that you have completed the functional rehab program. You can move again, you can move with greater ease, and you can move with a lot less pain. Your body has made enough of a recovery that you can return to work, and you can do most of the things you used to do.
Some people are content with just restoring their functional selves. Having no ability to move or having limited movement for months and then being able to move again is satisfactory for them. If it is not satisfactory for you, you can continue rehab and do rehab exercises that will have you walking and moving without assistance on your own again. That is what going beyond functional means for patients who have been in a car accident and want to restore themselves.