Much sympathy and ((hugs)), from someone who seemingly annually has to deal with the knees in one incarnation or other. Darn things start to wear out...
Okay, up the stairs is better. That's a sign. You really need to take a minimum of a week off to let this settle (dang). And do keep that Chopat brace in mind - it's not a brace as much as it is an alignment support. Widely available online, just google. We got ours (have 2) at footsmart.com.
We need to keep the knee thread going and help each other out. Last winter, I got picked off (while STOPPED, top of run waiting for clearance, doing zip!), and I did a slow sideways fall, not enough force/torque to release both bindings (one did). Oh, that was a stretch. Yeah.....2 grade-2 LCL sprains

- also left outside calf, ow. Really thought my season was finished (late Feb). I was in a FULL immobilizer, hip to ankle, on the left leg with the 2 sprains, supposedly for 3 weeks, ha - I lasted one, but that was apparently enough "rest" to get it going. Some PT, and I was good to go. Had a FABULOUS mid to late season last year, mid-March to early May
Are you doing any leg raises that don't involve the knee? Will keep the quad muscles right around the knee strong. Weight your ankle once you can hack it. Do sets.