Hi, you are having the knock knee, even before you are a good footballer, and was playing football well, with out any trouble. It is a psychological effect, as you had an
injury . You may get the injury, or any one in the team can get an injury. So it might not be due to the knock knee.
Practice
yoga, and
meditation, to over come this feeling, and if you became confident you can go forward. Dont forget any one in the team can get injured though they are not having knock knee. Thank you.