Characters A and B are identical twin brothers. B goes away to a British Boarding School, and doesn't contact A while he's gone. After a bit of soul-searching, B decides to return to his brother in the USA. The main reason he decides to return is because he's gotten sick/hurt somehow. He's scared that something will happen to him while he's away, and wants to be with his brother.
1.) Is there some sort of disease that would affect character B's legs, or put him in a wheelchair temporarily? I don't want it to be permanent, but I need him to be off his feet for a while, and maybe using a crutch for a while after. If there is such a disease, what are some other symptoms? How is it treated? How common is it? Basically, anything you know about it.
2.) If there is no disease that fits my criteria, would a car accident do it? If he hurt both legs/knees/feet or something, could he be put in a wheelchair/have limited mobility?
3.) Would someone in character B's condition be allowed to travel from Britain to the USA? Would he have to stick around for treatment instead?
I didn't really know what to Google. If you have some names of diseases/injuries or any other information that would help me, I can go from there.
Thank you all for your help in advance!