When you tear your ACL, patients often feel a sudden pop and their knee will give out from underneath them. Usually you will feel very unstable after the injury, as though your knee is “floppy”. Many patients will experience significant swelling and pain. The swelling and pain will gradually resolve. Without treatment, many patients continue to have discomfort and difficulty walking. It is important to see an orthopedic surgeon to make sure you have your knee addressed appropriately.