About 12 days ago I had ACL reconstruction surgery using a hamstring graft and a meniscus repair. Yesterday while I was doing my exercises and bending my leg, probably close to 90 degrees, suddenly it felt as though there was maybe a pop, or I'm not even sure if you can call it that and I'm not sure what to call it. But now when I bend my knee there is a new sensation and its as though I can feel something sliding right below my skin on my knee. When I bend my leg, it feels like something is sliding down over (maybe a ligament or something?) then when I straighten it again it feels like its sliding back up over it. It feels weird and uncomfortable and when I bend it enough times it brings me pain. If you can understand what I'm talking about, does anyone have any idea what this could possibly be or had it happen to them? It would really bring ease to my mind to know what this could be.