Could my knee have possible scar tissue left from when i broke it 13 years ago.... my knee keeps popping when i run and then gets a bubble of fluid ?

Orthopedic surgeon: There could be a problem with ligament,tendon,cartilage,etc. An orthopedic surgeon would be best qualified to evaluate and advise you.

Scar tissue with age: Only 3 years and you are experiencing symptoms that perhaps could be part to the normal adolescent growing period or from the injury as and early adolescent. I would have some imaging tests ordered and strengthening with rehab or Phys Therapy. Exercise is great for the longer but we want consistency and safety.