knee injury

so basically like 2 or 3 years ago i had my meniscus surgery, it was torn, afterwards for about 1.5 years it was ok, but about 8 months ago, this happened, when i put all my weight on my bend right leg(like sitting on a possitive angle, just on your leg, no hands) my knee pops, it feels like it dislocates, but just slightly, i start feeling a lot of pain, and i cant fully extend it, then through pain i extend it, and it pops back in, then for a week or so i still feel a lot of pain, but i can walk/do everything normally. it happens, only when i put pressure on my bent leg, i have been to some good doctors and noone knows what could be the problem. if it's not accurate what i wrote, please ask some questions, really need help on this one.