I Have Been Diagnosed With Arthritis In My Knees, Severe

I have been diagnosed with arthritis in my knees, severe enough that replacement surgery was recommended. I was given steroid shots 2 weeks ago and the symptoms have gotten better. But tonight, my worst knee has suddenly gotten MUCH worse. I can barely walk. I'm using furniture to support my weight as I go from room to room. I'm a widow, living alone.
It's midnight; is it likely that a night's rest will make things a little better or should I try to reach the ER? I have taken the full amount of my prescribed codeine for the day.