Hi, About 45 Minutes Ago I Stepped Up Into A

Hi, about 45 minutes ago I stepped up into a truck & something under my knee snapped. I have a lot of pain under my knee & down the calf....& cannot put ANY weight on it. I had an injection in the knee over a week ago for pain assuming it may just be arthritis....it was 100% better the next day. This happened suddenly without warning or earlier pain. Im afraid it could be a torn miniscus & trying to decide if I should go to emergency room tonight or wait till morning???? It really hurts & can hardly move my leg without lifting with my hands. I'm a 59 yr. female.