Back in 2011 I played football and that year I hurt my knee. After a play some people were still rolling around and I was standing strait and then a guy landed on the side of my knee it was my left knee. picture my knee bending all the way and touching the ground. It made an L shape. It was very painful and 2 days later I went to the doctor. They took and x-Ray but got nothing. Now the reason I'm posting this is because today. 3 and a half years later I still experience some pain. Every now and then my knee will buckle real hard. And also if I do squats etc. I have a lot of tension in that knee( apon doing the squat). I also have pain if I touch the spot where all of the pain used to be. On my patellar tendon. Now it only hurts when I touch the part that attached to the bottom part of my leg. I've never been able to find out what it was and I'm sure a knee injury wouldn't have effects this late. Does anyone have any clue what could have happend. And when the injury happened there was a very loud pop. It was hit from the outside not the inside.