My Son Is Only 21, He Works At The Airport

My son is only 21, he works at the airport as a baggage handler and the other day he was walking to his car when all of a sudden he calls me and tells me he could not walk or feel both of his legs from the knee down. I didn't know what it could be so he waited a little while and he was able to walk bug had a limp on his right leg. Then he was better but complained his knee hurt. What could it be? Thanks