Recently While Surfing I Was Pushed Backwards By A Wave

Recently while surfing I was pushed backwards by a wave and landed feet down on the sandbar.It felt like my knee inverted slightly foreward at which point I felt a sharp pain on both sides of the knee as well as behind the knee.At the same time of impact I heard a pop. It took a few minutes before I could walk.My knee was swollen and tender for several days.The swelling has gone down and have done the icing/elevation as recommended.Thinking all was good I surfed a few weeks later only to have the same incident repeat itself and suffer the same injury.Outside of going to a doctor what is your prognocess?