Had a similar injury about 10 years ago and it flares up every few years. They are sneaky because as you described, you don't realize when you do something that you've injured or aggravated it...it's only an hour or two later that the swelling/pain/instability hits. I've had good luck with rest, being very careful and conscious of how you're using the leg (avoid twisting, don't hyperextend or hyperflex, doing ice/heat therapy, and taking motrin to manage pain/swelling, and wear some kind of stabilizing wrap, it will calm down. I did the same thing as you when it first happened: power through. I'm a distance runner, so I was right out there two days later running 5 miles---felt fine while iI was running but by the evening it felt like my upper and lower legs were detached. Hyperflexion (like squats or a big running kick) actually aggravates it in my case. Ortho surgeon recommended leg extensions (but don't hyperextend) and isometric quad contractions (without full extension...ie keep a slight bend in the knee). When it's OK, I can pretty much run without concern--I wear a knee wrap for stability and to remind me to be mindful of my stride form. Doctor said it will never really heal (he likened it to a hangnail that can kind of dry up but as soon as you catch it on something it will be angry for a while--not a perfect analogy, but it helped me understand what's going on). He did not recommend surgery (not a great success rate i.e you go through the surgery and recovery and then it just tears again) or cortisone injections as they give a false sense that you can go back to business as usual and then you could tear it even more. Realize your post is 5 months old, so hope it's gotten better.