Question - knee problem (instability with football)

one and a half month back i was playing soccer...when i try to defend the ball with my foot...i suddenly twisted giving a Crack sound...i was in a lot of pain..after few minutes i tried to walk...but after few steps my knee became unstable and my knee moved medially as if the femur is out of the joint!!!

later that day i cant even walk properly..i couldn't stretch my leg nor bend it..as it was extremely painful...i took rest and applied ice...swelling is gone...but now after one and a half months i can stretch my leg completely but cant bend it completely...my knee still becomes unstable when i play football..

help please