Knees are fickle little bastards. I hurt mine jogging back in about 2011, I was dumb and didn't immediately ice it when I got home and it swelled up and I more or less couldn't use it for a week. Doctor said it looked like a sprain.
For about 6 months I had issues where it would seem perfectly fine, then when I put weight on it it would just give out on me. It still hurt on and off for about 3 years after that.
I didn't feel comfortable really pushing it again until last year, when I did my first 4000+ foot mountain after training for a few months, and I want to get back into running but I'm terrified of messing it up again.
For reference, I'm "only" 30.