04 stratus power steering

i own a 2004 stratus and i just went out to move it because of snow storm ...i had to put it in reverse to back out of the driveway i was turning it around to back it into yard and when i got in street and put it back in revers ..reverse wouldnt work ..but thats not all ...power steering suddenly doesnt work... went and got stepson to help get it outta street and reverse now worked ...but power steering still doesnt ... is it possible that its just too cold?...wife seems to think so ..but i doubted her ...i havent been having any kinda problems leading up to this .. the fluid doesnt seem to be too low ..but its dark out and i cant necessarily see if it might be a tad bit low which i seem to think that wouldnt stop the power steering ...unlesss it was terribly low ..im saying if anything it could be about 4 oz low ...not even half a cup lol i have read that the u joint under the lower shaft or rack could be frozen ..is this possible and how can i check it ..and also i read ball joints could be bad ...how can i check them?