Yeah, my story is relevant here.
After I tore my ACL, my knee did not hurt too much, and was not too unstable. In fact, I skied the rest of the day and the rest of the trip (after about an hour sitting in the lodge).
I was almost a "coper" -- if I had stayed in shape, maybe I could have been.
But htere was one particular loading direction that made my knee go out. It went about once a year at first, maybe three times the last year. I could feel it move, but there was no pain at all on these subsequent incidents.
So I talked to my General Practictioner about it at my regular physical exam. He spent a long time manipulating my knee and decided it felt stable and he thought it was ok. (I think this was before the year it went out 3 times.)
But then I tore the meniscus on my only ski day last year, and that hurt with an intense burning sensation.
So I finally went to see a specialist, an orthopedic surgeon. He said it was virtually certain I had torn my ACL as soon as I described the injury to him, but of course we needed to do tests to confirm. We did XRays to make sure no bones were involved.
Then he used the "KT-1000" which measures how far the doctor is able to displace the joint by pulling on your leg. It is quantified as a difference betwen the two legs. Anything over 3 mm (IIRC) is diagnostic, mine was 11 millimeters.
The morale is to see a sepcialist. Even with the best of intentions, you need someone with the experience to really understand knees.
After that, I had an MRI both for confirmation and to guide the surgical planning. (As a point of interest, the surgeon said looked like the stub of the ACL may have healed onto the PCL.)
I had surgery the last day of January 2013, did guided rehab for about ten weeks (I forget exact number) and continue to get more exercise than ever before in my life.
I got a brace recently. The consensus on their utility appears to be "it couldn't hurt."
Last weekend I had my first day back on skis, and it was glorious. There is a trip report on the site.
I waited almost a year to ski on my surgeons recommendation. My knee felt pretty darn good after 7 months though - I was tempted to go windsurfing, but resisted.
It seems to me if that if your knee was going to heal on its own, it would have by now.
So see a specialist, press for imaging, stay in shape, lose weight if you need to, and get better.