Knee injury...can YOU help?

in june last year i was on a trampoline and my left knee popped. it was quite loud but the pain was gone after a couple of minutes. i was limping for a week with pains coming nad going. i didn't go to the doctor, i begged my mum but she said it was no big deal. so i was fine for a long time and i did sports over the summer. i came back to school played basketball and my knee started hurting really bad. i noticed my left knee looked a bit funny as it was a wonky and it hurt, i went to physio but it didnt really help. my right leg was fine but after a while i felt it started to get relly crushed every time i walked. and my right knee started to go wonky, i dont know why but it did (btw that was the leg that didn't get injured) any theories on what is wrong with me. thanks! btw im 15 and i injured myself when i was 14.