I am experiencing knee pain. i have a bulge which appears on the left side of my left knee when i'm sat in a certain position.

This bulge in your: knee may be an effusion or collection of fluid in your knee. This may denote inflammation or infection, depending on whether you have pain/ heat/ redness in the joint. You may also have a hematoma or bruise on the outside of your knee that is more pronounced in appearance or pain when you bend it. The best way is to get a proper examination and diagnosis from a healthcare professional.