Possible causes of sudden knee swelling on the outside of the knee. No pain. Slight tingling sensation. Wasn't injured. Feels like it needs to pop?

Knee Pain. Pain on the outside of the knee is not very specific. Is that the only symptom ? Some people have a plica which is folding of the tissue within the lining (synovium) of the knee. It will sometimes cause a catching or popping sensation above the joint line. It is a difficult diagnosis to make unless you can reproduce it in the physician's office. I would monitor it and if it bothers you call md.