Knee sprain. If so would i need surgery?

I fell four days ago, when my foot planted my leg twisted and I felt my knee pop two times. I felt pain instantly and I was unable to walk soo I had help to my car and I went to the ER immediately. They did an X-RAY , and I was told that nothing was broken that it was just a sprain and to follow up with an orthopedic in a week if I still had problems! With the insurance I have I can only see a specialist if I had a referral from my PCP so I went to see my doctor and she was trying to examine my knee to see which ligament I tore but it was too much swelling and I am unable to bend it! Here it is four days later and my whole leg is swollen from my knee to my foot and I still can't bear any pressure on my leg. They gave me a knee immobilizer but it makes my knee so uncomfortable all I can wear right now is a wrap, could this be a ligament tear or is it just a small sprain if so would I need surgery? The ER doctor thought it was my meniscus.