Swollen knee. super swollen but no other symptoms. doesn't even hurt, not red, don't remember banging it or twisting it. what do i do?

It Depends: On what is causing the inflammation in the knee. Common causes include trauma, infection, inflammatory arthritis (gout, pseudogout, ra), meniscal tears, arthritis, and other ligament/tendon tears. A thorough physical examination and x-rays by your internist or orthopaedic surgeon can help narrow down the differential.

Get checked: There are many no. Traumatic things that can cause knee swelling. You should get it checked because significant swelling is not normal. I don't want to just speculate as some things are benign and others are not. Consider a rheumatologist consultation. A good history, blood tests, and possibly a joint fluid removal for inspection are probably the best first steps.